The problem is, this spin on things isn't so much of an interpretation as it is head-canon. Quinn was not being forced to do anything. He honestly thought siding with Baras was the best thing for the Empire, and more significantly, for Quinn's career. He thinks he owes his career to Baras AND he thinks Baras is going to be the next Emperor. He just wants to be the Emperor's right hand man, which is as high as a non-force user can go in the Empire. The dialogue in the betrayal scene spells out his true feelings very clearly. Basically, he's an ambitious little weasel and incapable of feeling anything very deeply.
You may also want to look for youtube videos of his comments to the other companions in that scene if you happen to bring them in. Very telling.
No, he's not worth keeping, sadly.
Personally, I adored the character when I thought he was what he appeared to be, a loyal, competent Imperial. Had I been the writer, I would have had Quinn drop you a secret message before you go in. "I'm going to betray you. Baras is watching. Let's put on a good show, eh?" Boom, problem fixed.
I've enjoyed two seperate warrior playthroughs and watched countless youtube videos describing the incident itself, actually. I ultimately played it the way that made the most sense to me, anyway. There is so much that isn't captured in the in-game scenes, enough I can only assume the developers themselves left it fairly open-ended so that we could RP it ourselves, shrug.
However, given the fact we KNOW that Baras is a master manipulator AND a liar AND a betrayer AND the sort of fellow who'll pull whatever string he possibly can in order to further his own goals -- it's simply not reasonable to think he wouldn't coerce Quinn into doing as he wanted. Also, given the fact that Quinn does NOTHING through nearly the entire game that paints him as anything less than truly respectful of the warrior, even loving if the warrior is a female -- i.e. he didn't attack the warrior, fail the warrior, stab the warrior in the back, try in any way to undermine the warrior, and certainly didn't try to kill the warrior even given the numerous opportunities available in which he could have -- it's perfectly reasonable to assume he was coerced.
No way to know what form that coercian took, mind you. There are any number of coercive tactics that Baras might have employed, though. Having watched Baras turn a man's brain into a puddle of goo, though, I don't imagine he would've (1) hesitated or (2) been kind about it.
Finally, if we're to buy into the notion that Quinn was coerced, it's not unheard of to consider that ANYTHING he had to say during the events on the Transponder Station was complete and utter hogwash. Either he was putting on show for Baras, if that's what you want to RP. Me, I tend to believe he said whatever he had to in order to make the warrior angry, because that's easier for him to face than her being hurt. It's totally up to you.
But regardless. Play your story as you choose to. I thought the story was an awesome consideration of the byplay between the Sith and the Imperials, what happens when a non-force-sensitive is caught between two Sith warring with each other. To me, the entire tale provides an interesting look at the social dynamics of the Empire as a whole.
Because, honestly. How does an Imperial officer really, truly tell a Sith "No" without being destroyed right then and there? And then if he does say "yes" in order to avoid being destroyed, how does he get out of it, if it's not something he wants to do? What exactly does he do?