I don't personally think that long-term/romantically they would have worked out, but I would have loveloveloved to see them interacting more as friends. I think they could have developed a lot of respect for each other.

I understand a lot of people's love of Faith/Xander...but the only one of his relationships I think really, really worked was his with Cordy (which I ADORED). With Anya, there was too much of a power imbalance, and I think he took her for granted. Cordy would never let him do that.