Hmmm... a female Midorya could have worked unexpectedly well... I mean, there aren't too many things that would really change in-story by changing their gender other than whom their romantic interests might be and... one large factor.
They might remind All-Might of how *his* Master was, seeing her in Midorya all the times a lot more than he does currently. It could create an interesting personal dynamic...
Though watching a girl constantly break her fingers and arms might be a bit much for some people... It is already painful enough to watch the male version do it, I can't imagine how it would affect the more squeamish audience if he was a female. >_<
