clearly the gameplay should be pretty different from now,anyway a well made fight game with a motion capture would be awesome.
The objection that someone can't do martial arts is a bullshit:is full of dance games on kinect xbox,but only 1% of the people who play them can replicate 100% that moves.You have just to replicate more or less them.Same would be for any kicks(for example if you give a kick while you are turning on yourself,even slowly,you can give a side kick etc.)
And if you are fat and can't move for many time,so...your problems!