I don't like this. Your suggestion would make paralyzation resistance the easiest thing to get. You could scum for necromancers in the wilderness and get a ton of ghul corpses. And after finding some basic herbs, who cares about sickness and poisoning, or paralyzation on an empty field?
Paralyzation is dangerous and there should not be an easy way to get it intrinsically. (Yes, there's always pools, but it is a gamble.) Also it puts a quite nice tradeoff situation to the later game if you don't happen to have any other means of paralyzation resistance and need to use an amulet of free action instead of that cool amulet you would have.