Morse could go off on his own expedition out to the colonies looking for answers much like Amanda Ripley in Isolation. He'd also look to uncover other shady aspects of Weyland-Yutani. This spin-off wouldn't have to focus only on the aliens. There could be other story threads like the Auton synthetics, general synthetic revolts, Prometheus related elements.
I agree that there probably isn't much interest in this sort of thing among the powers that be at 20th Century Fox. I just thought it could be a fun spin-off. If not a TV series, maybe a novel or comic book. If it did happen as a TV series I would guess they would cast a younger actor now to portray Morse. He's not nearly as iconic as Sigourney Weaver's Ripley. Hey, if Sarah Connor can be recast then Morse probably can be too.