Isn't Hicks relatively unique in the canon in that he pretty much just believes Ripley? From the word go he is listening, and is unlikely to attribute her stories to space sickness (as Clemens, entirely reasonably, might). Where the other Marines are bull headed he is quiet and contained. Which is an interseting thing to play in that world. Someone level headed who out and out agrees with Ripley, and someone capable who doesn't contradict her instints, but rather enables them.
And his is an experience (were he to survive) unexplored in the series too. We've had a person lose fractious crewmates and a child to time, but this is a person losing real, genuine camaraderie but also gaining a new unit. The idea of the surrogate family unit in a world that knows these things exist - Does that make you more or less out to exterminate them? Ripley never has anything to lose after Alien (especially after Hicks and Newt are killed offscreen). If Hicks's sole function is to present a different side of her - a woman with a lot to lose still after these things - then that is still import enough.
And take it to Earth War places, and there are opportunities for conflict in how these survivors deal with their survival. There are stories to tell here that could justify this decision, as long as it isn't just done for the sake of it. From Fox's point of view it makes sense to draft in a fan favourite who could shoulder future films should Weaver want to bow out too. It's not like Michael Biehn is going to refuse a high profile series after getting stiffed on A3, T2 and Avatar, is it? There's money in series, and familiar faces bring audiences back.
I wouldn't put his odds high on surviving this one, mind. It's card trick thinking, innit? Everyone will be so wary of the fact he dies in A3 that they'll be certain he'll survive this one, which means Blomkamp is likely to undermine that certainty for shock effect. Although, I can see Hicks living on with Newt while Ripley finally goes (which is super pointless as they did it in A3, but there we are). Conjecture is the best.