This. But on top of that I'd wish they'd see the potential in a complete overhaul of a character just for the concept of MvC3.
Just as an example, take Akuma from SF. You could take the fact that he's the obvious powerhouse (plot-wise) of the series and actually change his moveset a little to reflect it. I say this because the overall strategy and feel between a series of games is obvious. If you look at Ryu (another good example for this) as he plays in SF4, TvC, MvC2, and even the Alpha series he's a different beast each time you see him. The key difference is while that movelist is familiar with many people, it doesn't always translate well into other games. MvC2 being the big example, and even moreso since this is the series we're talking about, since the zoning games played are on a whole other level from the SF franchise. Thus, keeping their old movesets tends to nerf them without actually applying any nerfs to them at all. Same goes for charge characters in the MvC series, but that's a whole different story.
Back to Akuma. You could actually step him up a little and he'd be a viable replacement for the likes of Captain Commando. Take some of his old supers from previous games and make them standard specials and he'd have a decent zoning game. Even taking something like his Misogi, creating a vertical attack out of it (similar to, if not exactly like CapCom's AA Assist), and making it a standard special would be a large step in converting a SF character into the MvC play type.
All theory and stuff of course, but I thought it'd be neat to talk about.