[quote=@Bonjour xx][@Kalas]
Given that his character is now an outlaw from his people...
[/quote]
Okay, stick with me here, 'cos this one's really messy. Mez's parents were killed as traitors, leaving him as a ward of the Lords indirectly responsible for their deaths. What if the treason they'd committed had something to do with helping smuggle Thuboisii through Visipian space? That would mean that Mez's rivalry was more to do with a deeper hatred of her people rather than against Marga herself, at least at first. It would also mean that the Visipians would have to be portrayed as more xenophobic than initially described, but this could always be included as part of the religious mania.

After he'd learnt the truth of his parents' fate and fled to the mercenary outpost he crossed paths with Marga and after performing a few merc jobs together, where he acted as cover for her more subtle forms of combat, the two became lovers. It wasn't until they'd been 'warping the frontier' together for a while that Mez discovered Marga's mixed race heritage and found himself repulsed at the thought of having soiled himself with a Thuboisii halfbreed. In a fit of rage he tried to kill Marga, only for her to escape him and disappear from his life.

Now, after many years apart, the ill-fated couple find themselves drawn together again, and Mez must come to terms with his feelings for his former paramour. Will he be able to overcome his racial hatred for his former lover, finally being able to accept her as she is, or will his ingrained hatred of her people drive his to make another attempt on her life?

And my having re-watched [i]Code Geass[/i] recently and just remembered Villetta/Chigusa and Ohgi's relationship had nothing to do with me making this suggestion. By the way, if you haven't seen that anime I'd recommend it.