Okay! Acheron's canon--Dark Hunters--is super easy. Nick Gautier, assuming I can use the YA prequel series as part of it. I would seriously have already done it if the playercest wouldn't kill me, but I am too attached to Acheron to give him up to do it. At that point, he's all snarky and charming and adorable and oops, a secret half-demon of the SERIOUSLY EVIL variety except that he's actually a good guy himself, and it's like. Sort of FIGHTING AGAINST HALF HIS NATURE, and sob so many layers I love him so much. Bonus points for being a manga/video game nerd ICly.

Angel Sanctuary! I'd cry and cry and cry and beg you to let me keep Katou. BUT NO, I CANNOT IN THIS HYPOTHETICAL, so! Zaphikiel. Blind troll!angel with SO MANY LAYERS and a secret badass side. WHAT'S NOT TO LOVE?

Glee! ...Well, since you said that it could be somebody someone already has, Jesse St. James. Except I would not be even a millionth as amazing at him as Juri is.