Generally speaking, for terms of balance, I would call the skeletons incomplete and require that he finds new skeletons. Once it has been damaged beyond its life, there is no chance of reconstruction because the fundementals of what made it no longer 'are'.
But if you're looking for realism, you could have a d6 chart for limbs/torso/head and get him to roll on that to see which parts are damaged. Then maybe he can combine the skeletons to re-animate them.