the animation for up-air is very close to being quick enough to end before Mario lands from a short hop.
I would not want to change his short hop height of course, I believe all it would take is making his up-air slightly faster, which I dont think would break anything.
I think it is the PERFECT way to give Mario a very small buff without changing anything about his character. it also adds some more bonus technical depth to Mario, which is not a bad thing. It is something you could learn to incorporate into your game, such as shine grab with spacies, but it would of course not be necessary to use.
I am not good with frame data stuff, but I like to think I am pretty good with the feel of things in melee, and I think this would feel right.