I think the past is the past. CoH2 had a rough start but look at the situation right now, the game is great.
Just don't burn out from the beginning all the people excited to make your game great. AKA don't shoot yourself again.
In the case we get CoH3, i don't want to see the same mistakes/decisions done during the first year of release and having to wait 2/3 years for the game to be in a good state.
I don't think/want balance done by the community exclusively but using mods/test server to try them before releasing them on the wild should be done without exception. How many bugs had been discovered by the community? How many of them have also been fixed by them?
Mod/world builder from day 1 pls. Work a bit more with mappers and have a constant map rotations of them. Just to avoid complications, you could have a "global" ban (so you don't waste bans) in these kind of testing maps if you want but let them be on normal automatch rotation. Once enough feedback/popularity is gathered, some of them could be part of the permanent rotation.
Gameplay wise:
-Hotkeys
-NEVER AGAIN STUPID RNG (AKA every plane crash tells a story). Moderate RNG use is fine. 1% chance of collapsing a building because someone snort inside, is not good.
-Commanders:
First of all, NEVER AGAIN the whole disaster as the current roster of EFA commanders.
Amalgamate from coh1 and coh2 system. We could have TOP 6/8 commanders (FOR ALL the lifespan of a faction) which have around 6-7 abilities which must unlocked. You don't unlock all 7 of them, cause you will have to choose from one or another ability at some point of the tree. Tree structure could vary. Ex: you could either have early, mid or late game alternative choices depending on the commander.
-Emplacement/Automatic i win button skills-units => Please no.
Monetization:
The system we have now is fine and would had solve the whole "P2W" commander release up to some point. If you want to let your creativity go wild, why not recover the whole theatre of war. From what i understand, the whole Co-OP mode on Starcraft 2 is more popular ATM than the whole sum of all the multiplayer game modes. If you want to release stupid Tiger Ace/Windustry YOLO commanders, do so for those game modes.