When Germany invaded France it had pitiful tanks. They were upgraded afterwards into the fearsome, powerful, version of the Panzer that we have in AH.
Putting in the Char B1 bis would be like adding the Sherman... Weak and vulnerable -- only there were 50,000+ Shermans that served in action, and I'm guessing only a couple hundred Char B1 bis'. Might as well just add the Sherman (*shrug*)