I'm here to give some suggestions involving some commanders. Out a subject that excludes commander, but have involvement with suggestion and think it will not disturb.
Fortification Doctrine is a doctrine that specializes in defense. However, this doctrine has an ability, that's can use in the attack, and that is good, not being IeFH 18. But where are you going? I'm trying to express that doctrine help well on the defense, but I think that also helps well in attack, so this unbalanced. Not sure they used to attack (history), etc ... But ability Zeroing Artillery, my suggestion, which can only use in allied territory.
Other change that I wish in this doctrine, instead, Field Defenses, has new passive skill, that instead of being able to build wooden bunkers, may be able to build bunkers of concrete.
Concrete Bunkers will be more expensive. However more resistant. And so differentiating, even more OKW.
Stuka Bombing Strike
I think Stuka Bombing Strike ability, have to be changed. Put some fires (think) on the floor where skill was used. Increase munition costs, cause problems (disabling and leaving with little HP) in the weapons of Emplacements (in mortars, dies crew becomes abandoned).
Now off the subject commander. But involves suggestion:
Suggestion: Kubelwagen have a ability, for remove of the battlefield and gain some thing with this. But without if benefit, after of training one. But why? Because I think this unit is only good at Beginning, soon after I think it becomes useless. So when you takes the best, this moment, you can dispense it, and gain some resource with this.