I had this idea:
The movie takes place in between Alien and Aliens, about 42 years after Alien. A distant colony, founded by the United States, begins to revolt. They start an uproar and there are constant riots. The Colonial Marines are sent in to quell the rebellion.
But before they get there, some Preds deploy a queen egg, and all hell breaks loose.
But before all hell breaks loose, the Marines arrive and have an epic battle with some rebels. Meanwhile, the Queen starts laying eggs and then Xenos spread throughout the colony. They start out like Giger's Alien, a young adult. Then they mature into Cameron's Warriors. There are also some dogs on the colony, so some Dog xenos are thrown in too.
Then the Preds arrive. They all look different, like each are from a different clan, like a joint-clan hunt. There is about half a dozen or so.
So then a massive battle begins! Eventually whatever is left of the Marines, and Rebels, have to team up for survival.
But the Company discovers what happens, and they activate some sort of protocol in the synthetics. So a synthetic tricks the group into wandering in the nest. One of the Rebels is impregnated by a Facehugger. The synthetic takes the rebel and abandons the others, and takes the rebel to a hidden ship. The synthetic puts him in hypersleep and escapes the planet. The Marine's ship is sabotaged, due to protocol, and the humans are trapped.
Eventually the colonists are all killed off, and the Marines go out in a blaze of glory. They are all killed, the last Marine is killed by a Praetorian
Eventually, the Predators fight their way to the Queen, and in an epic battle, kill her. They take her skull, but the rest of the Xenos converge on their location. One Pred escapes and sets off their bomb-thingy. They had planted several throughout the Hive. He sets them all off and kills all the Xenos. The Pred flies away without the Queen's skull, but plenty of human and Xeno warrior heads.
After the credits, it shows the synthetic and several scientists all looking into a small chamber. Inside the chamber is a Giger Drone, curled up in the corner.
Then the shot changes to a blood covered wall. We here MU-TH-UR, she says "WARNING QUARANTINE IN EFFECT" and "SPECIMANS LOOSE"
The camera pans to show several scientists and staff cocooned and being turned into eggs.
And instead of AVP3, call it ALIENS VERSUS PREDATORS
EDIT:
Forget the very ending....kinda crappy.