Here ya go.....
A. charmed one instead of becomeing a charmed one is called as the slayer and buffy instead of being called as the slayer becomes a charmed one.
B. Takes place after the distruction of Sunnydale and many slayers are called all THREE charmed one's are called as slayers as well as being charmed one's.
Slayers with magick? oh boy.... the mischief that can be had.
Thats all there is to this challenge.
A.Must have a charmed one and the slayer.
B.Must have the charmed one's and the slayers.
so a combo ...