As far as I am aware, Merids is right. Based on the facts that 1) ghosts are not corporeal, so creating something like a spell would go against they, and 2) they are not susceptible to wand magic(that's just poltergeists right?) so that I believe would eliminate them being able to create it as well.
Just as a note, Oz's sheet ^^^ is an awesome example to look at one take on making a ghost playable within a (mostly) human RPG.