Have the fang gang make an appearance...can't you just see Cordy as Adelaide but I think Angel makes a much better Nathan Detroit than Xander; plus Xander and Spike really haven't gotten along. And hey! Angst galore for Buffy, Spike, Cordy, and Angel. Or you could have it set just after graduation and have Angel return. Doyle and Wes would be excellent gangsters as would Gunn. But do what you want...