The single smartest revenue choice GW could make would be to farm all its former Specialist games over to FFG. They'd make Battlefleet Gothic really work, finally. But that's far too smart for GW to do, and HALO will be pwning the market soon enough.
Battlestar Galactica would be fun, but rally its just a single box-set worth, having only two factions and limited minis.
A Babylon-5 revival would be cool - I still feel so burned from Mongoose's fumbling of the product. we still have all of Stephan's CTA sheets and stats though, and I still have my Centauri, Drazi, and early EA for games, not to mention every cardboard ship cut-out ever.
Bab-5 could only happen if JMS got off his jaded butt and made a real deal for the show to live again.
As for the others, never enough factions or designs for new games. And some of those ships were awful. Though I'm fond of BUCK ROGERS, that starfighter was so lame I remember trading my old toy of it to a friend for some Micronauts.
FARSCAPE is about the only IP with a ton of alternate ships, but everything was a little too spazzy, hand-waving biomechanics, and more about people than ship fights, for there to be a coherent game.
I'd still adore it if someone could crack the realism of Honor Harrington or The Expanse series into an actual playable game.