Undeploy Hex:
Beginning with the 3rd map of preludes u will notice a hex at the border of the map with a white dotted line labeled "Move to Reserve".
If u move a unit on that hex it will be moved into ur reserve and u can use the freed core points to place another unit next to a supply hex(town hex with a circle).
The unit u moved to reserve can be brought back to the map in the next turn provided u have the needed core slots avail to field it.
U can switch heros, repair to max in one go, upgrade to other unit/modell with units in reserve.
Especially replacing fighters with bombers after achieving air superiority is a fast and easy way to use these new hexes.

new Random heros:(currently in Preludes and 1939, will be added to the rest of the campaigns one by one)
at the start of a scenario, where u don´t get to buy a special hero with commendation points, u get to choose a random officer out of 3 categories. A weak one for 1.000 prestige, a mediocre one for 3.000 prestige or an outstanding one for 5.000 prestige. This replaces the random hero generated at the start of a scenario.
here are the hero-traits sorted by categorie:
weak:
AggressiveCounterattack,Avenger,CounterBattery,CombatLuck,Distraction,DoubleMassAttack,EntKiller3,ExpertSupport,Exterminator,FastLearner,FastRetreat,FearsomeReputation,FlagKiller,
FerociousDefense,FierceFighter,FirstAid,LearnsFromMistakes,NoRetreat,NoSurrender, Resilient,RiverAssault,SixthSense,SkilledRecon,SkilledSupport,SuperiorManeuver,ThoroughPreparation,Unyielding,TenaciousDefender
mediocre:
AimingAssistance,Butcher,CityFighter,CripplingBlow,DoubleSupport,DoubleMove,EntKiller4, Evasive,ExpertRecon,Famous,FieldRepairs,FastRebase,IgnoresZOC,Liberator,Leadership, LowProfile,PhasedMovement,Readiness,TankKiller,ReducedSlots,Survivor
strong:
ArtySupport,ATSupport,DoubleAttack,Envelopment,FastDeployment,HitAndRun, IgnoresEntrenchment,LethalAttack,LightningAttack,MachineGun,OverwhelmingAttack,Overrun,
Provocator,Legendary,Scavenger,ShockTactics,StrikesFirst,PreciseOptics

Each trait has a limit per campaign to reduce unwanted hero clustering due to unlucky randomness. Currently this limit is set to roughly 1 per year of the war.
This should result in a wider spread hero variety.

Some heros have further restrictions:
ZeroSlots,Camouflage,IncMaxOverstrength,NoRetaliation and Vigilant are currently restricted to 1 per 2 years. This can be bypassed with the General trait "Killer-Team".

FieldRepairs,SkilledRecon, FastDeployment, FastRebase, ExpertRecon, CounterBattery and FirstAid are restricted to the apropriate unit.types to reduce player puzzlement.

Enemy Air reinforcements:
Starting in 1940 Hannut hangars will be present on several maps. As long as those hangars are around the enemy will get air-reinforcements if they loose planes.