Wow the prototype was great. The gameplay mechanics were amazing.
I would definitely buy this game if it was a full game. Not sure what approach you want to take like comical-fun story/sidequests or like a slightly more serious tone with some fun sidequests. Either would be cool though.
Only thing I would say is I don't think there is a need for a run button. I think a walk feature would be cool (since you may be on a tall building and don't want to fall), but I think the walk should be the one you have to press down.