Update on the plan...
Just to give a short feedback:
Over the weekend i worked out 3 Teams of 4 Marines each (to provide the different pre-made chars for a one-shot - rolling up a char for each player takes so much time usually

).
I also worked out those neat small predators which will be coming to the planet to become blooded.
And then, yesterday, i got a new book: Chaositech (by Monte).
And lo: The colony is a new mining camp that tries to extract a newly discovered material (which will be, basically, raw chaos) for a company, while a second company tries to take over. The marines are sent to keep peace (at least keep open conflict at a minimum).
When the chars are right in the heat, caught between two rivaling mercenary factions, all people who were in touch with the new material will start to show signs of mutation (as in chaositech rules).
Shortly after the aliens show up, and the Predators, too. The mess should be complete...
So it's not only Marines vs. Aliens vs Predators, it will be MUTATED Marines...
I only hope this won't be too much for my players...
Dougal