Pretty sure it has to be guss, all the jedi girls are romanceable so cant be them, and truly i think Lord Scourge is far to important to reduce to an Alliance Alert Recruit.
Maybe that's false hope but there is an argument to be made he knows the emperor better than anyone and is the most 'powerful' companion in the game
will be incredibly disappointing if he becomes a sideshow, especially when you consider the love Scorpio is getting