My friend wanted to play a Hoodoo priest (basically the same thing but voodoo is the bad version of hoodoo.) The way we did it is we had him take part of the true believe template, like Guide My Hand and Bless This House, but also gave him Ritual (Hoodoo). It was a thematic limit, so you'd have to trust your player, but it gave a very fun feel to his character.
This was for a feet in the water game, so I don't know what other powers would fit at a higher level, but the ghost/spirit possesion thing is pretty cool.