My idea is we should deviate from Earth and took a place on a new planet. The story should be the Predators hunted the Military personnel on the planet but because of some breach the previously static Xenomorph in a hidden chamber started to wreak havoc. This time there's no "Enemy of my enemy is my friend", and this is a kill or be killed world. I would love the Predalien return and maybe the Runner. I would like a team up of the Drone and Warrior caste.
I agree with the statement that the Marines must be likeable and not a cardboard character. The Aliens also must to be a serious threat and even made the things worsen, like killing a few Predators or impregnate them. The ending should be the Alien conquers the planet, but at the stake of losing their Queen in an airstrike, the Predators left the planet because of being outnumbered and seeking a new hunt, and the Marines with some survive and returned to Earth, maybe with a twist that one of them is the host of the Queen.
My suggestion is there are epic battles of Drone or Warrior vs Predator, and many of them , not just one epic Predalien or Queen fight. I think this should be rated R. The Predator design should follow Anytime's design or Pussyface's.