Yeah, Zayne's outfit was in a Cartel Pack for TOR, so that's a resource someone could draw on. It's been awhile since I read the comics, but Zayne's story ends as he's kind of drafted into the Republic war effort, so Republic embassies would be my best idea of where to place him. It's also very likely that he decided to step back from all the wars after seeing what his friend Malak becomes. Either way, any dialogue featuring should definitely draw on that prior friendship. I would also like to see Jarael in the game (whose outfit is also in TOR), possibly by using Nadia Grell's TOR face model with different long hair attached. For KotOR 2, I really don't know if Zayne fits. He would have to be in hiding and very secretive about his force sensitivity, lest he draw Nihilus to him. Or maybe he goes to Telos to hang out with his ol' bud Carth Onasi. Oh, and if you have Carth in your party in KotOR 1, it would be very strange if they don't interact with each other...
This of course would all be a huge undertaking.