There are many people who suggested T4 buffs, such as Brummbär getting more armor or more range (it was hit by a double nerf), Panther getting more accuracy on the move and some adjustments for the Werfer (though that was suggested by a minority).
Considering that Allies got lategame buffs through the bank and considering Ost is the lategame faction by design (small squads, no light tank) this wouldn't make them OP but is the very minimum I expect for Ostheer.
Best buff is free medkits for pioneers and Grens once T4 is up, as well as a 250mp Hauptmann officer squad with 5 men with Kar98s, supervising armour repairs to boost repair speed on an individual vehicle, air recon and call in artillery.