ohhh ok, i think my early post has nothing to do with this new info xD. I mean how can someone develop the nervous system, i mean i know you can train it in aspect like coordination and reaction etc., but thats more like using its latent potential, not building more, like in the case of muscular mass.
Back on topic, maybe adding a hidden stat that keeps track of the turns spended on doing something and the increase the linked stat, like running/throwing things dex, crafting/reading/building/dissasembling gives something to dex, int or str, based on how involved is the stat on certain activity