Bingowings said:

Better killing them all off in one off screen moment to set the mood of the film really seeing as Ripley herself was going to die.

Still not convinced that there were not other alternatives. :)

Let's see how that could be: Ripley wakes up in a medical chamber; She finds out that they crashed on a prison planet with Hicks and Newt. Few days before, Newt was sent in a place for lost Children on another planet, after verification of her identity . They don't understand why they are still kept in this prison but they discover that Weyland Yutani paid the prison's boss to keep them locked, the time for them to send a ship. Hicks is sick. Alien burst from him at key moment. Movie plays more or less as the original Alien 3 from that moment. Not sure that it sets the mood as well as the original Alien 3 (you're right about that) but at least it would have given descent ends to two beloved character from the previous movie.