How about a BV206 / BVS10 style articulated trailer behind the tank / AFV? It could actually improve the mobility of the vehicle its attached to as well as being capable of carrying pretty much any payload required including additional fuel for the tanks. They could even be designed with quick connect / disconnect couplings so the tanks can drop them off before or on contact to provide supporting fires. Apart from SPAAG and SAM you could also have automatic heavy mortar, pioneer, engineer, logistics, even a vegie bin (APC module) for assault troops to provide close support for the tanks. These trailers could also be fitted with their own propulsion to permit them to catch up to the tanks post contact. They could the armour equivalent to the infantryman's pack / Bergen.
Totally impractical but fun to model.