It would be cool to get a DLC pack that allows to modify the tanks. Since the M20 Armored Utility Car is an M8 Greyhound variant.

Also allowing us to swap up the M4 Sherman to build its variants. Same with the Panzer II allowing us to turn it into the Marder II or even the Wespe Artillery. Adding side skirt armor sheets to the StuG II to turn it into the Stuh 42. Or even allowing the SU-76i to be made, since the russian designed them off captured Panzer III & StuG III tanks.

Examples for the M3 would be:

Self Propelled Guns
T12/M3 75mm GMC
T19 105mm HMC
T19/M3 81mm MMC
T30 75mm HMC
T48 Gun Motot Carriage

SPAA (Annti-Aircraft
M16 Halftrack (Dual 50. Cal M2 Brownings)
M17 Halftrack (Quad 50. Cal M2 Brownings)