Hmmmmm, I thought Giles spoke to Buffy when Faith arrived on the scene and told her that Faith had an "unstable" reputation previously as a slayer. I know she (Faith) relocated to Sunnydale when Buffy "died", but I understood that she had been training/patrolling somewhere else and her watcher was killed as well. I will have to go back to the season with Faith and check my episodic guides (talk about fanatic, eh?)
And with Dawn having been "the key", I am sure the writers can come up with some sort of "transformation" to a slayer-type (even using Buffy's last "death" that she was retrieved from). Oh well, I was disappointed that the Spike character came back so deranged, disoriented and well, rather wimpy, but we will see. VERY interesting "EVIL" though (a mix of them all) and prophetic wording that we shall be returning to the beginning....hmmmmmm (again).