I like the idea I think it has TONNS of potential, but I think you've made the blurb very specific, if you want to turn it in to a like a proper RPG system (I'm not sure if that's what you want maybe I misunderstood) then you have to make it a little more flexible. Whast you have written is almost like uh..a module to a system sort of thing.
The idea of the spirits I like a lot, I could make a couple of more suggestions, but I odn't know how much you want splashed over the board or PMed, Or even if I'm making any sense.