Hidden body sounds too OP. Crystal Caves will become the scariest place in the game.. A god alternative is turning you into one of those transparent phantoms at all ranges. You know, the ones that appear randomly or when you touch a bloodstain (in demon's souls they were red).
I already use Chameleon as a staple PvP spell. Nothing quite as amusing as slowly stalking a guy as one of the tree people things in Painted World.
Add in the occasional people that do spot you and point at you with a gesture and the people that just walk up and attack you not realize you can parry straight out of chameleon and you get a great time.