I've never liked playing as the characters that change soo that wouldn't really make me happy. I mean, it's great for you Mr. I like to play as Zelda and Sheik and they change so I'd be used to it... Damn that's a long name.
Anyway, I'd want Raichu to still be fast but maybe have an even slower and stronger version of thunder and more physical attacks (Like thunder punch and mega kick) but eh, that's just what I want.