Just a cool thought for a feature of this game, since there is the lcd on the pf and I seem to recall some talk/possibility of side panel screens on the side of the cabinet? I don't know if that's verified, anyways, my idea is that when the ball drops into a subway, maybe the screen shows the alien in a duct, and the possibility of a game mode where another ball drops into play while the subway ball is held and you have to make shots to shoot the flamethrower and push it back. If you succeed, you get 2 ball multiball, if you fail, the other ball pops out and back into play (possibly with some penalty? I don't know)
Maybe we are past that point in development, but if you could implement that it would freaking awesome and would really capture what, especially, the first alien is about. Since you listed that there will be multiple modes possibly, with alien and aliens included, if you're in Aliens mode you could sub the flamethrower for the auto-turret.
Anyways, while I'm going to wait to pick this game up until it's released, I am very excited about it and look forward to the upcoming details of it.