Well, wouldn't mind an idea similar to this...but well, can't say I like a few things.

[s]though, but I don't have time to write up my thoughts at the moment.[/s]

Bee just pretty much summed up my own thoughts xP
Although, I have to say you're assuming that spirits are treated badly after being part of this Guild/receiving this mark. We don't really know that, since we don't have enough information in that regard.