Are you making a suggestion rather than talking about something actually in-game, or is this actually in-game? I'd rather not see this in-game. Or in general really. I've been around for awhile and I've seen these same two jokes that never go anywhere about short characters repeated ad nauseum for the last 40 years and now I'm sick of it.
If its just an excuse for giving something to oppai loli fans, I don't really care, lol. They're starved for content as it is. In that case, as long as its optional, I see no reason to object. Though, I will say doing something like Ikuya Daikokudou's Kinpatsu x Kyonyuu ni Henshin De is something I could get behind a lot better. (And could possibly serve as inspiration for content.)
Basic overview of manga is this:
So, to translate that, Toph has some body changing things to try and force confidence. After some events, she becomes comfortable with her real body, but occassionally likes to pull the body-morphing stuff back out just for variety.