The reason I kept it at 45 is to lower our expectations and to encourage critical thinking and decision-making to ensure our additions/removals really counted. We cannot just haphazardly add/remove characters. The first choices, the ones with keeping all 35 characters, are conservative and dull. The last choice, the one with keeping 25 characters and adding 20 characters, is too liberal and can be a good thing or a bad thing depending on who gets cut and who gets added.
EDIT: I liked the MvC3 roster. Sure, there is no Mega Man but I got my Amaterasu, Haggar, and Arthur.