I know there are a lot of people out there who think that this can't work as a relationship. Both have too many issues, both are wrong for one another. I don't agree with that at all - just because you're not perfect doesn't mean you're not allowed to be in a relationship. Sometimes people make it sound like the 'recipe' for a relationship that works is one party has issues and one party has no issues. Is that really a realistic scenario?
Someone pointed out that Quinn's a crap human being - he's a deadbeat dad, he kills people for a living, he has anger management issues …
Turn it around, he doesn't want to kill people anymore and there are a lot of people who are notionally in the line of killing people for a living. This doesn't automatically make him a bad person. Police, members of the defence force, executioners, covert ops/black ops personnel - these are all people who are 'sanctioned' by the law to kill people in certain circumstances … not a job I'd go for but I wouldn't say that it automatically makes a person bad. People are a composite of different things. I think it depends on whether you think certain things will put you beyond the path of redemption permanently.
The deadbeat dad thing is probably a more difficult one to get around. I think the only defence I can put up for him there is that he probably did regret his actions but by the time he did, it was too late and it would have been more selfish than not to try to re-inject himself into his biological son's life once Julia, her husband and her son had established a family and a life together.
Carrie truly believe that she couldn't be in a relationship because of her issues - she's gradually learning that that's not the case. Having a mental illness does definitely put a very heavy strain on a relationship but it doesn't mean that it's not possible. The thing in favour of this dynamic is that Quinn knows about Carrie's mental illness before he opts into wanting to be with her. I think it can be different when the mental illness is discovered after a relationship has commenced.
To me the biggest obstacle to Carrie and Quinn being able to have a relationship is the fact that they are fictional characters in a television series that will want to maintain drama and suspense …
It's hard for writers to keep a romantic relationship compelling and interesting over more than one season. The formula is for the antipathy and antagonism to signify sexual tension. There's a belief that an established relationship/marriage is 'boring', so the temptation is usually to make relationships stop/start .. introduce misunderstandings, infidelities, jealousies and all sorts of other obstacles. Soap operas are the worst for this but any long-running show is the same. By the time you get to the nth season, all the characters have paired off with one another at least once or multiple times. It's death to a romantic relationship.
I think the Maggie Q version of Nikita was a little unusual. That show ran 4 seasons. The Michael/Nikita relation started out conventionally. Antipathy became sexual attraction which became hate and then it became sexually charged again. Interestingly, the show-runners decided to let the couple get together in the mid to late stages of the FIRST season. There was a brief, very aborted attempt to bring in some sexual tension by introducing the character of Ryan but that was ditched quite quickly and Michael and Nikita remain a couple through the entire series. They're friends, they're lovers, they work together beautifully and I loved that they were completely supportive of one another and for me the relationship never got stale.
The show was cancelled after season 3 and season 4 was only allowed to have 6 episodes. Accordingly, the show-runners let Michael and Nikita have a happy ever after ending of sorts.
The only way I can see Carrie and Quinn being permitted to have a 'happy ever after' ending is if one of the following happens.
1. Season 5 (maybe 6) is the last season. That way the writers don't have to introduce lots of complications into the relationship because there is a definite end to the series.
2. Carrie and Quinn exit as main characters at the end of season 5 or 6, the series is rebooted and a new cast is brought on - with Carrie and Quinn coming back now and then as guest stars …
I can't see the Carrie-Quinn relationship being able to exist if the series is envisaged to continue for e.g. 10 seasons.