I'd love that. There is no cool evil Sith character you can romance. All the flirt option I had so far were with non force users, Theron, Quinn, Andronikus etc.. (yep, i only play empire)
I know we have Arcann but personally I dont like him that much and I always end up killing him.
And yes, Malgus killed his twilek non force user slave wife....because he saw her as a source of weakness. But how can we be a weakness to him after we beat him back on illum, saved the galaxy from Valkorion and other op stuff we did.
I think the story now has a potential to make it happen. I really hope they will. Malgus is just so cool.
Otherwise I will have to choose Khem Val.... (yikes haha, rip my assassin