I actually like the current system in which you don't know whether body parts contain skills. We shouldn't take every surprise out of the game and make it purely systemical. Games need some magic and some things we don't know from the beginning.
I though like the idea of the alternative use of body parts. But that should come at a cost, and not only a monetary one. For example the necromancer could demand that you give up a part of yourself (like skill or ability points) for the possibility to gain new skills consuming the soul of a dead person.
