That's some DEEP stuff you are talking about there. First of all, forget latex for the mask, it would have to be silicone. You would have to mold it yourself to add metal hooks with a flat base to be molded into the silicone around the mouth. The mechanics are beyond explaining here. Lets just say, to do it right, nix the 3 axis skull and head to a machine shop. The main parts are the "pinch actuators", to pinch the sides of the lips into an "O" or stretch them out for a "smile". Secondary are the "snarl" actuators, to pull up on the upper lip, and thirdly is the lower lip actuator, to open the lower lip even with the jaw closed. Never had a client with budget for that so I've never built one, but I have seen it done by a couple of other people and it's pretty complex. Not a project for the beginner, that's for sure.