Gotcha, might not be as involved but you may want to check out some of the Dark city games by facade games. The general theme on those is 2 or more factions pitted against each other with some social deduction because you don't know who's on which team. Those are generally fairly quick and easy. Secrets is another similar game. All of those were pretty fun and sit a large group too.

As for Nemesis, yea, it is a bit of a time sink. I don't think I've ever unboxed and reboxed under the 2 hour mark - even when it is just my friend and I moving briskly. That said, certainly give it a shot on Tabletop Simulator. It's one of my favorite games because how the game reacts to what players do, which just sets chaos into motion.

Tabletop Simulator has tons of free games available, and they are all done very well. Certainly a gem. The idea of subscribing to make a game playable is kind of weird but makes sense after a bit.

When I think of BSG, what comes to mind for me is something like Panic Station, or maybe Human Punishment (the Beginning). Maybe take a look at those three games if you don't know them already.