I think you're looking at something that's basically non-canon (as in, there's no real hints on how to do it) until Ghost Stories comes out.
THAUMATURGY [–3] (page 275)
SPECIALIZATION.
Anti-security magic Complexity Bonus +1.
I notice that Dad's Spirit has Thaumaturgy but not Evocation. I would imagine that, as a Warden, he would have needed both, and that, as a Spirit, he would retain both or neither, but if there was a game reason to keep it that way, no problem.
I think the GM ruled that since he was of spirit he couldn't cast Evocations and used that refresh to give him the Spirit Form powers. I imagine if he was a PC when all this went down he would be justified in rearranging his character to a great degree.
That makes sense. How has his ability to perform Thaumaturgy been handled?
in our campaign we have a player who plays the ghost of the kitchen girl of a world war II russian submarine.
I like the idea of a disconnected spirit and will present that to the PC as well.
Pardon me, the WWII Soviet Front is one of my favorite history subjects so I'm going to take this on a minor tangent and go history geek for a moment. I know that women served in combat in the Soviet Army during WWII but I didn't know there were women submariners as well. I'm curious if the player had any scholarship to back the concept up or if it's something they just made up. The book that was in sounds like a fun read. :-)
I think a ghost PC is a brilliant idea. It's a character that I wanted to do for our game but it got nixed because of the disparities with ghosts in the books. I'm biased because I've never read the books so I don't have a strong tie to the canon but to me in a world with magic and the supernatural practically any rationalization of why the character is a ghost is legitimate.
Given the forthcoming book, and the chapter of it already published on the web, I find it extremely difficult not to call ghosts canon in any case.