Stormageden would be a decent NK target for the vig tonight if not one-shot. Although Rubik himself suggested it (probably to stave it off, in a reverse psychology kind of way), I don't think vig should target Rubik; maybe if it were a lesser player, but he's good enough to be useful, and there's a small chance he'll be targeted by scum anyway.
And yeah, I don't recall ever seeing a game in which the survivor or similar third-party alone wins upon survival, and the description posted in the set-up explanation clearly indicates that other factions can win.
A survivor wins if they live
he can win with Town
he can win with Scum
He can win with third party
He can win alone
as long as he is alive. he wins