The way it looks from my limited knowledge is that ghosts are uncapable of personal magic because Living Djed is involved, for example if someone were to cast a reimancy fireball they would take the living djed and form it into rez. Which means as a ghost I would need to assume a living host in order to cast that fireball should I have known how to do it. What was interesting in reading the text concerning Leeching for me is that there is no statement involved that says what happens to foreign djed when it has been stripped from a living thing. Does that djed die? If the djed dies does that become a crude form of soul mist?
When asking that question a secondary question emerges the main question, if the process of Leeching does not require Djed in order to be used would a ghost be able to use it to draw in foreign Djed.
It would seem that leeching would actually be rather useful for a ghost.
After stumping the chatroom I was asked to place this question here for a person thats a pro at magic and could help me get the answer that would sate my curiosity.