Chris had an ammo system in MVCI. Personally I'm not a huge fan of that style of play. I like having a lot of tools available and then trying to figure out how/when to use them.
I'm also not big on stance switching, other than my Mans Siegfried in Soul Calibur. I don't think Mega Man in Marvel 1 and 2 needed that, if he could just use the special weapons he had from the get, he'd be more fun in those games, but it's not too weird.
That said, a stance switch character could be neat in Smash or someone like Noob Smoke, strictly from a mechanical standpoint, not a "Aye mayne, I REALLY WANT *INSERT CHARACTER NAME HERE* in Smash." standpoint.