The idea of inflating/deflating a balloon you're floating on is very interesting. But in the current game I don't see any reason not to keep it at its minimum size. Perhaps it would be cool if you're outrunning a floor that raising (with lava or something like that) and you have to balance the small size, which is a smaller hitbox but takes you up slower, and a large size, which takes you up faster but is more dangerous because of its larger hitbox. Something like that could flesh out the concept and balance it out more. That said, it was an interesting idea and a cool take on the theme, nice work.