+0 is my vote, but I think -0 is not unreasonable given that it exists already at +0 and has no relevant char-op applications that I know of. Maybe on a marshal cohort so that they can do their auras without having to worry about getting attacked?

I prefer +0 to be safe. There are a lot of monsters that this thread is adding to the pool of playable races, and only a few of them need to have a critical mass of actionless powers in order to be viable as disembodied spirits. I'm not sure which monsters, but I can easily conceive of their existence, and I'd rather be safe than sorry.