Target Audience
This post is aimed at other Mod Developers

Post Objective
Scout's Progress severely modifies the scout (and pathfinder) unit, as well as implementing additional units as a unit progression path throughout the eras. This may lead to complications in combination with other mods. Further, other developers may desire to make use of some of my work.
This post is intended to give some intel on how to do so.

Version
Latest Update is for Patch Version 3
I'll write up the one for Version 4 when I get the breathing space to do it properly, as there were quite some changes.

Unit Handles
Three new units, and their respective handles:
Explorer* - UNIT_BETTERSCOUT
Ranger - UNIT_RANGER
Special Forces - UNIT_SPECIAL_FORCES
*I wanted to use 'UNIT_EXPLORER' for the Explorer Unit, but BNW had problems with that
All other naming conventions have been kept (Unitclasses are like "UNITCLASS_BETTERSCOUT", etc.)

Localizations
All string references are named thus:
TXT_KEY_[Object-Name]_[Attribute]
Attributes are:
Description: DESC
Civilopedia: PEDIA
Strategy: STRATEGY
Help: HELP

Example: TXT_KEY_UNIT_BETTERSCOUT_DESC
Exception: All Big Muscles promotions reference the same strings (Example: "TXT_KEY_PROMOTION_BIG_MUSCLES_DESC")

Promotions
Several Promotions were added. These were assigned thus:

Big Muscles 1-4
ObjectKey: PROMOTION_BIG_MUSCLES_X (X = 1-4)
Assigned: Directly assigned to unit as free promotion.
The promotion that makes scouts so badass tough when defending.

Blitz
ObjectKey: PROMOTION_BLITZ_2
Assigned: Tier 3 Scout Ability (Survivalism, Scouting or Sniper)
Blitz was cloned from the traditional Blitz, as the XML structure would not support sufficient PromotionPrereqOrs. If you want to add additional PromotionPrereqOrs, start at 4.

Deadeye
ObjectKey: PROMOTION_DEADEYE
Assigned: Directly assigned to Special Forces
The primary reason why Special Forces units are so hideously expensive to build, in terms of construction points.

I See Dead People
ObjectKey: PROMOTION_I_SEE_DEAD_PEOPLE
Assigned: Directly assigned to Special Forces
Grants recon, same as planes (unobstructed sight range, 6 fields out, unless you use mods that modify recon range).

Sniper 1-3
ObjectKey: PROMOTION_SNIPER_X (X = 1-3)
Assigned: Selectable unlocking ability in 3 tiers.
This was implemented in an a bit weird way: Since only Rangers and Special Forces get a ranged attack, only those ought to have access to the Sniper Promotions. Sooo, I needed a unique prerequisite and was a bit lazy. Only Rangers and SFs have the invisibility promotion assigned to them directly, which is why I decided to make that the prerequisite (as PromotionPrereqOr1). So, if you want to add another prerequisite, just add another such condition, starting at PromotionPrereqOr2. The other requirement is the Unitclass Recon, so if anybody ever introduces a Submarine that is termed thus, it too will have access to the Sniper Promotions if used in combination (You could also choose the Terrain Expert: Mountain Promotion, which would be a bit odd, but far less gamebreaking).

Invisible Submarine & See Invisible Submarine
The scout tiers get those Promotions, even if it is a bit silly, when you read it. Not because I wanted to, but because adding the same properties to a differently named Promotion will simply fail. Shucks.
So yeah, SFs get to play submarine. Must be Seals.

Survivalism
ObjectKey: Unchainged
Assigned: Unchanged
This promotion was overhauled, removing standard defensive boosts (Scouts already have enough and the small numbers were meaningless in comparison), and giving powerful ranged defense boni, to make it competitive with the other two promotion tracks (So now you get to choose between Exploration, Defense and Offense with fairly equivalent Powerlevels, so it's an actual choice).

Terrain Expert
ObjectKey: PROMOTION_TE_[Terrain] (Terrain = MOUNTAIN, FOREST, PLAINS, TUNDRA, WATER)
Assigned: Tier 3 Scout Ability (Survivalism, Scouting or Sniper)
Same as Blitz2, the first 3 PromotionPrereqOr are used, if you want other promotions to unlock them, feel free to add them at 4+.

Design Philosophy of Promotions
I created these promotions the way I did, to not only make scouts competitive (which I think I managed to pull off), but also to make choice matter. If there's a perfect choice, it's not a choice: It's a necessity. Furthermore, I wanted to make these promotions to have an actual Impact, on how the player can use the unit. In some cases that worked well, in others slightly less so. Your choices certainly affect in what terrain and role you want to use the scout.
The scout also gained lots of powerful abilities, so I tried to look out for balancing factors, a way to make sure I did not just create a super hero unit, better than any other unit. Most helpful in that regard was, that the very low base power and the immense power boosts for defense made any attack power Upgrades relatively meaningless. A Morale Promotion with +15% Power is all nice for a mechanized infantry (90 + 15% = 113,5), but not all that impressive on a SF (20 + 15% = 23).
If you want to make a mod of my mod: Please refrain from fiddling too much with the base power of the units. They would likely become gods or trash. For example, I initially had given the SF double the ranged power (the sniper promotion was proportionally weaker). 40 RP doesn't sound like all that much, right? But it's used for ranged defense, which, combined with the Big Muscles Promotion and Survivalism 3 meant +600% defense power (or a total defense of 280). That's a LOT Stealth Bomber strikes.

Conclusions
Feel free to implement support for my mod. If you decide to reuse my XML ... well, a contribution in the credits would be nice, but feel free to use it.
If you have a mod that could be more meaningfully integrated from my side, give me a comment, or post it in the Discussions, I'll check out the Mod and see whether I'll do it (Don't expect immediate action though, I lead a busy RL. Trying my best to accommodate is all I can offer).

Cheers, and thanks for managing to make it to this point,
Bosparan