There’s already two unique M4 variants in the game that barely see any use. Why would a third one make any difference?
There's 5 in total, standard M4A3 Sherman, M4A3 76(W) Sherman, M4A3 105 Sherman, M4A3E8 Sherman, and the Calliope.
This Jumbo would be a 6th variant with more armor, hp, slower and with the same 75mm gun as the standard Sherman but no shell changing, at least in my mind.
It would be easier to balance right now than the Bulldozer for Urban Assault and would provide a new and unique useful tank for the new commander that many people want, plus it arguably fits the theme better than any other unit. Of course that if you're assaulting a town you'll want to send in your most armored tank to support your infantry, and not one equipped with a bulldozer blade lol.
Also another picture of CoH models of the 76(W) Sherman and Jumbo from a mod:
Barely any difference is noticable besides the gun.