Not the final comprehensive update, but nevertheless a significant one.

-Thannhausen now owned by Biberach. Turns out the entire existence of this state in that province was my misunderstanding
-Thannhausen province renamed
-The 'Weissenau' owned by Tirol has been renamed
-San Pellegrino renamed
-Celje now more restricted to their core immediate principality. To balance this, their development has been increased to higher than it ever was before, they have been given cores around Krain, a better ruler with Skanderbeg-tier stats, and the Habsburg cores on them have been removed
-Habsburgs now have missions to conquer Celje and Trent
-'Free Vaud' mission restricted so ten+ states don't end up taking it every time
-Romagna flag changed and made easier to form, should appear in most games
-Pruthenia easier to form; can now be formed by TEU immediately if they lose all of West Prussia
-Major development nerfs in Austria, Styria, Tirol, Venice, Milan, Burgundy, Flanders, Holland, Poljica, and Modena
-Development buffs to Ferrara, Mantua, Genoa, and Hum
-Spoleto starts with cores on the three new Papal provinces in the south
-Carniola switched to Slovenian culture so it can actually be released from Styria
-One more Carinthian core added
-Macerata starts as an Italian Monarchy now
-Papal vassals switched to Marches
-CB of Sforza Coalition changed to almost ensure states are released in the peace deal
-States released in Sforza peace deal should immediately become Papal marches
-Camerino now starts as March under Papacy
-Abbacy bonuses changed to reflect their extreme lack of large armies. Abbacy gameplay will now be focused around Mercenaries until one secularizes or falls to government rebels
-Free City increased coring cost idea replaced with spy defense. Because of their developments, by a century in it was costing 300 adm per province to core them
-Genoan Traditions slightly buffed
-Waldensian religion map spread nerfed to be more relegated to the Alps
-Netherlands province revolt random events now fire less often
-Experimental re-addition of the since-removed Trade Company Regions. The entire system has been reimagined to represent the Donation of Constantine, which cannot be added to the Empire (though some provinces start as Imperial in 1444) but can be turned into trade-boosting Fiefs representing the de-facto autonomous states under nominal Papal control. This deserves more Flavor Events and some further tweaking of bonuses/restrictions, but for now just the basics are added
-Poland, the Prussian cities, Fiume, Croatia, Dalmatia, Poljica, Hum, Ragusa, Albania, and Durazzo all Eastern Tech now
-'Overseas' CB from Expansion ideas fixed up, now gives any Western nation a permanent CB on the Easterners/Ottomans
-Invasion Nation bonuses nerfed quite a bit
-A handful of Culture changes to reflect the contours of the Alps
-Ceva changed to Ligurian culture to reflect those changes
-Vaud now Historical Friends with the rest of the Swiss Federation, gov changed to Canton
-Hungary no longer Historical Friends with Austria
-Color of Ottobeuren changed to pop less; Lowenstein to contrast with Pfalz better; Irsee to contrast with Tirol; Celje, Carinthia, and Carniola to contrast with Styria
-Major rebalance of certain Imperial opinion modifiers - the Annexed a Member of the HRE malus and Unlawful Territory malus have been more than halved

MAP:
-Various province border edits, especially in the Papal States
-As always, various Positions.txt fixes
-Addition of actual well-researched Alps. The Alp wastelands were originally a complete afterthought thrown in based solely on CK2's Alp borders, and were continually scaled back. I know some people really don't like wasteland mountains, but this change was a long time coming - the importance of certain provinces as Alpine passes and the separation between certain states by mountains was highly important to the development of Italy versus the HRE; plus Colored Wastelands will take care of the more egregious bordergore, especially if you conquer full present-day borders
-Addition of the one-pixel wall around the entire playable map to prevent giant wasteland colorings like Rendsburgian Denmark or Austria-Hungary in the 1460s. Because of this, you now can and should turn Colored Wasteland on
-Significant adjacency changes between Ursburg and Wettenhausen, Baden and Strassburg, various Alpine states like Savoy and Nice and Italians like Carpegna and Florence
-Significant fixes to province terrain; the most treacherous parts of the Alps are now all mountains while the flat northern parts are now hills/woods/farmlands, esp. Swiss capitals
-Various tweaks to Areas/Regions to reflect the contours of the Alps and more accurately portray the de-jure borders between the Papal States and the Empire
-Various tweaks to Trade Nodes to reflect Alps; fixed paths of several nodes through the alps

-Modena now a union junior rather than directly owned by Ferrara
-Ferrara and Modena colors switched to emphasize Ferrara's status as a Papal Fief

Small historical fixes and some attempted balance fixes.

History:
-Wurttemberg now correctly split into two lines, Urach and Stuttgart
-Urach and Stuttgart tags added
-Decision for these tags to form Duchy of Wurttemberg
-Papacy now controls three border provinces formerly owned by Naples
-Changed Savona's government to Oligarchic Republic in attempt to lower overall Confederation possibilities
(Northern Swabian region should be a bit more balanced now with that split)

Balance:
-Severely nerfed 'max free cities' such that tons have to be annexed before the Emperor can start establishing more
-Nerfed Free City automatic tax income from 5 to 4
-Nerfed Crown Lands from 90% Liberty Desire to 40%
-Forming Switzerland no longer auto-inherits all your subjects (which allowed really gamey WC tricks)
-Poland now Historical Neutral with Bohemia in attempt to prevent unbeatable Poland-Bohemia alliance
-Removed Cantons' ability to create confederations. This was originally added to allow for a Swiss Confederacy, but a lack of moddability meant it accomplished virtually nothing and instead allowed every OPM in the empire to join a deep alliance web
-Nerfed prestige from Imperial Immediacy and Imperial Knights. As it stood, you could get permanent 100 prestige almost effortlessly

Fixes:
-Fixed stray pixel near Ticino which allowed you to walk through wasteland
-Slight border/adjacency fixes near Franc-Comte, Geroldseck, Geneva, and Augsburg
-Fixed some Army/city positions, especially in Switzerland
-Elevate to Canton decision now impossible for Free Cities, to prevent cycles where the Emperor keeps granting Free City over and over again

Working on the mega-update I came across various historical inaccuracies. This is a small update to patch them up and fix a few bugs from the last update.

HISTORY:
-Aquileia owned by Venice instead of Gorizia
-Korcula owned by Venice instead of Ragusa
-Makarska area owned by new 'Hum' tag, only playable Orthodox state at game start
-Pico corrected to Pontecorvo and owned by Naples instead of Papacy
-Senarica owned by Naples instead of Senarica
-Wildeshausen owned by Munster instead of Bremen
-Northern Tecklenburg owned by Munster instead of Tecklenburg
-San Marino given specific named ruler
-Poljica given specific named ruler
-Hagenau name changed to Unterelsass, now starts as monarchy in PU under Palatinate
-Hagenau-Stadt name changed to Hagenau
-Krnov owned by Opava instead of Opole
-Sausenburg starts as Baden vassal in an attempt to make Baden less garbage
-Boosted Oldenburg development
-Boosted Brandenburg development
-Removed Papal cores on vassals (didn't realize they allowed instant annexation)
-Makarska area culture changed to Croatian
-Provinces at Frisian extremes changed to Frisian culture
-Sieben Komoin tag now Southern Austro-Bavarian culture

FIXES:
-Fulda, Stavelot-Malmedy, and St Gallen use their proper ideas again
-Theocracy Heir Events added for all but Papacy
-Envoy speed doubled
-Merelbeke renamed to Aalst
-Province near Cologne with anachronistic name fixed
-Typo which made Meppen use a Bohemian dynamic name fixed
-Map misinterpretation which led to two Wildeshausens next to each other fixed
-Meppen Area renamed to Tecklenburg Area since Meppen wasn't even in it
-Brussels position slightly lowered so it isn't right on Mechelen
-Bergen army position now correctly in the province
-Groningen Independence event should not fire for Frisian nations anymore
-Bohemia given more relation slots so they don't always have vassals declare indepedence in month one
-Hohenlohe's color darkened to contrast with Palatinate
-Swabia given more vibrant color
-Carinthia and Carniola given new colors to distinguish from Styria
-Imperial Knights estate influence values tweaked so they aren't breaking free all the time

Tons of small changes made over the last few weeks, some will probably slip my mind. I'll try to list as many as possible:

-Southern Italic culture group split in two, adding a Central Italic group. Marchigian, Latian, Apulian, Salentine cultures added
-Dalmatian culture added to Northern Italic group, now covers much of the Adriatic coast; also Tridentine
-Albanian moved to its own group (might have already done that?)
-New revolter tags added for cultures - Bari, Lecce, Ticino, Dalmatia, Durazzo (representing Angevin Kingdom of Albania)
-Seven Communes tag added, now starts with a province between Venice and Trent
-Minor province changes - removed some Wasteland mountains, changed the shape of Avignon
-Repurposed a province from Luxembourg into Stavelot-Malmedy (sorry if this causes minor exclaving)
-Various small changes to Italian Areas/Regions, including both provinces and names
-Multiple new Formable Nations: Emilia, Lombardy-Venetia, Arpitania, Magna Frisia
-More detail for Slovenian culture/country ruler names
-Two new Estates added: Utraquists (for Hussite nations) and Imperial Knights (for HRE members). The ugly and problem-causing exclaves of the Teutonic Order have been replaced by normal provinces owned by local powers which start with the Imperial Knights estate on them
-Utraquists will try to mess with your foreign relations but can do various services for you
-Knights will cause religious controversies but also have benefits
-Most significantly, the Hire Holy Order feature is now a function of this estate and is no longer based on culture. Hiring a Holy Order will spawn a random one on you, you wait for them to build up an army and then bring them to war. Once your first war is over, they will automatically re-integrate into your nation
-For those without Cossacks, there is an equivalent decision-based version, but the ducat coast is quadrupled to balance the fact that you don't have to deal with estate loyalty/influence
-Hamburg node has been merged with Lubeck node to boost its significance. This won't 'break' existing saves per se but you will finda hole in the trade map and might lose a Merchant if you were collecting there
-Several important border nodes (Bari, Napoli, Ragusa, Barcelona, Antwerp) now start with a 'foreign trade' modifier to represent the mass of incoming wealth from the ROTW
-Events over the course of the game for Barcelona and Antwerp to gain tiered 'New World Trade' bonuses
-Fixed various typos like the Shadow Kingdom saying 'Lombardyy'
-Dutch Culture event now just combines Hollandic and Lower Saxon
-Removed Unite Dynastic Lands mission until I can maybe figure out how to debug it
-Temporarily combined all the TEU 'prussian nation' events into one; in the future this will be expanded into a threaded system where your choices will influence how things turn out
-Added several new events:
Fugger family event, in the 1500s the Habsburgs controlling Burgau will usually grant it to the Fuggers
Haigerloch sale event, Habsburgs will usually sell some provinces to Hohenzollern
Angevin Inheritance event, in an attempt to boost France they will now usually inherit ai Barrois/Provence
Leave League War event, in an attempt to reduce lag small nations will now quickly peace out by event
-Burgundian Inheritance has been updated to Paradox's new system, meaning Aragon/Spain will often get it. This should go a long way in nerfing the Habsburgs and preventing rapid Imperial Reform passing
-Changed Prussian ideas almost entirely back to vanilla (they still have free reinforce as an ambition)
-Brandenburg now starts with a small bonus modifier to compensate
-Brandenburg now has a few Ottoman-style decisions which grant permanent bonuses
-Hohenzollern now has a unique idea set, sort of lighter Prussian ideas plus inflation reduction to compensate for their silver mine
-Mantua now has a unique idea set
-Group ideas for all Abbacies added, so they don't simply use Divine Ideas
-Several new unique idea sets in Italy courtesy of an Italian contributor; namely Fiume, Aquileia, and Seven Communes
-Hungarian Invasion event now only fires if the target does not have 100 legitimacy, so you can avoid it if you are careful
-Swedish Support event now properly removes their capital from HRE
-Invasion nations should now discover the world on spawn
-Modded Trade Goods with MEIOU images/descriptions have now been replaced with original ones
-Very small fixes for army positions and province terrain
-Swiss Nation requirements now based on tech instead of league war
-Re-added some French events
-Fixed problem with Prussian ideas not actually applying to Prussia
-Habsburg naval nerf modifier, can be removed if you invest in naval ideas
-Changed some province names
-Changed Unlawful Territory modifier from nuking your Legitimacy; now it increases AE impact

HOTFIX 1:
-Fixed a typo that made corruption stupidly expensive

HOTFIX 2:
-Cultural changes in Italy including new Rhaetic group
-Removed Slovene culture event, put Slovenian in game start
-Made Cilli/Celje an independent nation
-Kirchburg correctly under PU with Gorz
-Fixed some Bavarian localization
-Tweaked ideas for France, Prussia, and Spain/Aragon
-Nerfed Emperor bonuses slightly
-Changing from Catholic now correctly removes the Anti-Papacy modifier
-Fixed Orange being Waldensian by accident

HOTFIX 3:
-Reunited Helfenstein
-Fixed some city name errors
-Fixed Swiss region being named incorrectly
-Fixed bugged conquest missions (I think?)
-Raised unrest requirements for Free City 'help from emperor' event so it won't fire as often
-Raised base Diplomats and Diplo slots by 1 each
-Cut siege cycle by 2/3 and lowered outnumbering requirements to balance sieges for amount of provinces
-Added NIs for Stavelot-Malmedy, Fulda, and Saint Gallen, courtesy of Steam user Tnesniv Yørel
-Other small fixes that slip my mind