I think the key to this game being amazing is the way they chose to make the submission system. It should not be like thier wrestling game where a certain body part is hurt and when you attempt a submission based on how weak it is is wheter they will tap. THIS WILL NOT WORK FOR MMA. The way it should work is based on how you defend the move, and what I mean is this.
Lets say that when on the ground when hold one of the top trigger buttons you are defending. So if I hold down the top button and pressing to the left I am defending my left side (arm, face, left side mount), now if the person on top is going for an arm bar and I am defending it then obviously its a no go but If I try and go on the offensive and stop defending then the person on top should be able to make that move and get the arm bar. I doubt it will work that smoothe but if they can get it close then the game is a GO.