Mr Trick
Scooby
Thankfully I doubt they would have allowed Xander to give into Glory's demands in "Weight of the World" and betray Dawn the way Ben did in that episode. He would have gone out on a high note, and maybe assisted Giles by holding Glory back long enough to kill him. I would have preferred Xander die in this scenario no matter how depressing it might be. It has way more of an edge to it than miraculously splitting Xander and Glory at the last minute, and would give Giles and the Scoobies too easy a way out.
I'm more skeptical about Xander having Wes's storyline being legit. Would Xander have been moved over to AtS following "the Gift"? Would the shows become more crossover heavy, with Connor being the miracle baby of Angel/Buffy instead of Angel/Darla (which, even for my shipping preferences, is way too fanfic)? Either way, the mental image of Angel trying to smother Xander in a hospital bed is kind of awesome.
I don't know why but for some reason I just can't see Xander as a character on Angel besides like in a one off episode. I did enjoy the banter between Xander and Angel on Buffy, but to me that just seems like a subplot, and since Buffy isn't on Angel its not like there would have been a lot to build on with that. I think Wes was the perfect choice.