I've said it til I'm blue in the face, but Shaw's African dream sequence in Prometheus gives Blomkamp the perfect out. Just have a monitor on the Sulaco showing (in that exact style) Ripley 8 throwing herself off the gantry from Alien 3, or bald Ripley caressing the newborn and in one shot you keep the previous films in canon as hypersleep nightmares AND you tie the new film explicitly to Prometheus. It may not be completely satisfying, but it allows everything to co-exist. You can see Hicks and Newt's psyches wrestling too, to stop it being so on the nose (also handily filling in some back story for those characters while limiting clunky exposition). Starting in either sleep or dreams is a hallmark of the series, regardless. Aliens starts with a nightmare, after all.
Regardless of how anything fits, this is a logical play for the studio. While it may not be the absolute status quo here, there is a lot of public love for the first and second movies and their events. From a business stand point it makes sense to hark back to these as opposed to risking something totally new. Studios are not renowned for taking risks after all. Aside from that, Weaver isn't going to need this series forever (I'd be surprised if she survives this one, honestly) and having two characters in Hicks and Newt that audiences have already shown affection for to carry any future entries must be attractive to Fox.
And, from a purely sentimental point, wouldn't it be nice to see Michael Biehn finally get a decent break after all these years? If anyone could genuinely claim to have been put out by Alien 3, it's him.