Is this gonna be the alien (drone) version or aliens (warrior) version?
I'd go with drone, because you can put your head in it's head and still see.
Just make sure you have eye holes in the the skull under the clear carrapice.
If you're doing the warrior, then do what everyone else does. lol.
will the mouth move?
I saw a mask that can do that.
I've figured out the mechanism, but you may already know.
It's the sucky fox design, but you get the idea.