The chestbursting, skinning, head biting, dismemberment is next level violence from other IPs they work with. Somethings you can tone down - like when characters get shot in a Lego game they just explode into pieces then come back to life. I think toning down certain bits of violence in Alien or Predator would dilute it a bit too much.
Not being able to play as Lego Vasquez blasting Lego Aliens still makes me sad though.