What have we seen so far?
Alien: introduced egg, facehugger, xeno.
Aliens: introduced "the hive" and the Queen.
Alien 3: introduced the idea of variants (dog-xeno).
Resurrection: introduced the idea of mixed DNA via cloning, leading to "the newborn."
AVP: nothing new this time, except Predators can fight xenos like you or me fighting a wild animal.
AVP-R: introduced the Predalien (as a queen).
Prometheus: remember that guy in the chair in Alien? Let's make a whole movie about that! Too much to list, and the movie is awesome because of that.
Covenant: David is revealed to have either "created" or "re-created" the xenos. I like the idea that he was trying to "re-create" the xeno as opposed to being the actual origin.
Haven't seen Romulus yet.
What can "Alien Earth" do that hasn't already been done?
I want to see something new, radically new. Imagine a human on the side of the xenos, or a xeno on the side of humans? It doesn't have to be that. This is an example of "not done before," ya know?