I like the possibility of our baddie being Riley. I'm interested to hear what became of him. Right now I'm feeling that wearing a mask for a prolonged length of time could certainly make your neck itchy.
We might be assigning too much importance to a line that was meant to be quirky, not an actual clue. So I'm going over everybody in my head and trying to think of who we know who could attain that kind of power, and who would believe that the... is there a term for the transformation of all the potentials into slayers? Someone who believes that was a mistake, someone who would care about restoring the balance of the universe. The other possibility is that our bad guy is just in it for himself, and the stuff about the world being out of balance wasn't true at all, just meant to rattle Buffy.