Maybe it's my insane mentality, but putting Newt in that prison could have been REALLY interesting, first of all: bald little girl, freaky, right?  Second, they're all prisoners (if I remember correctly) and the idea of something as pure as a child being thrown into their terrible world could reignite their resolve to escape or damage their tough veneers, give 'em something to live for and then kill 'em all with an Alien.

Of course, I'm sure part of the reason Newt's not in the movie is she grew up too much for the whole "stasis" thing to make sense.

You could kill off the other guy halfway through or earlier, in man-on-man violence rather than an alien death, give him an early heroic out.

I'm sure it's contracts and more that kept those two from reappearing.  But what do I know?