Characters in most Alien/s films, novels, comics, and graphic novels rarely have the luxury of turning each other down for support. And I think that all four films had compelling reasons for (most) of the folks to stay together. In Alien, the cast was a ship crew with nowhere to go. In Aliens, Ripley, Newt, and Burke were the outsiders among a (stranded) marine platoon. In Alien3, you had the inmates of the prison in a mutually-loathing bond of brotherhood. And in Alien: Resurrection, it went back to the ship crew.
Most of the characters don't have any practical alternative to helping each other. Even if they hate the guts of everyone around them, the best they can do is wait for an opportune moment to screw everyone else over and take off into the darkness of space.
That occurred to me, but another interesting feature of the group dynamic in the Aliens movies (and in classic horror films in general, ala Night of the Living Dead) that sort of fouls up possibilities for Aliens and that I cannot get around is the fallibility of the characters. Ripley always keeps it together, and in Aliens / Alien 3 she had a few people with cool heads, but the other people in the group are freaked the **** out, like any actual person would be in their situation, and they make mistakes. Terrible, costly mistakes that only make their lot worse. Now, Obsidz has shown a certain willingness to let their characters have their own wills in the past but you'd be inviting a lot of griping from your average gamer if you follow the films in that regard. Players are used to having control. Horror is very much about having no control at all. I wonder if Obsidz would be willing to allow characters to die abrupt, passing deaths like they do in the films, despite all the player's best efforts. I admit I'm very excited by the prospect.