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.
So to extract these skills, how would you differentiate between body parts with skills and body parts without skills? Would it be some kind of interface in the UI which only allows those parts which have skills through, or would you have to try every one and see if any are useful?
I think that you could pay the necromancer to "identify" corpses for you. So you pay money upfront before you even know whether the parts contain skills or not.
Without the necromancer every body part you find should look the same, without categorization.
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.
No.
This would be buying an unknown skill book for gold. You can already buy skill books, skill books which you KNOW what they are for gold. I would never, ever, use a system where I sacrifice skill/ability points or body parts(!) for a skill book, especially an unknown one. That's simply not a worthwhile trade in any way.
That heavily depends on the skill. For some character builds it's pretty impossible to gain certain skills because they'd require huge ability costs. So getting skills by different means - circumventing ability requirements! - could be a very valuable trade, even if you have to give up something of value yourself in order to gain it.
