I still believe that OUAT will get the Charmed treatment and will continue as a comic series or after years it will return to TV. So how your S8 would have been guys?
I for one will try to think a bit like the writers... What I mean? My Villain for S8 would be Old Wish Realm Regina. This would continue Regina's story. I would also have her break Gothel's "tree" spell and use her as well, along with other miny Villains. Maybe she will try to acquire the Dark One powers and she succeeds in the end. Her battle with Regina will show again Regina's growth.Â
Also, other idea is Villains of the realms unite to take over the Kingdom of Regina at the finale setting S9 with a brand new Evil arising.Â