I think AT guns should be able to attack Vehicles - the fact that Recon Jeeps and Stugs are unable to be targeted is very odd! i don't think it would be too game breaking either to let them target them.
Either way, infantry are servery underused, would love to have some good infantry in game, Commandos perhaps? Regular infantry that have a higher attack against buildings?
Also i think the Bismark should be a league unit - just saying otherwise, maybe some submarines? can only attack ships again subs would be a league unit.
For buildings would LOVE to see a coastal gun be able to be built along side a turret for Harbors. Can only attack ships, but range is 350 perhaps.