Switching the cast would be a massive risk. The one they got now is clicking. Do we really want to lose Jessica Lange?
They need to do something big to rewrite the rules for S2, tho. A story about a bunch of ghosts trapped in a house won't cut it. It could be the Benny Russel twist; the antichrist's birth starts changing the rules and the world; there are portals to other times and places in the house; or something along those lines.