The neutral is supposed to be run in the same cable or raceway as the other conductors. From a practical sense I can see why running it tywrapped together using a non-metalic raceway, would not cause a real problem if you used the same entry to any metal boxes but it is not code compliant.
Just put a small plastic box next to the metal one and nipple in to meet the spirit, if not the letter of the code.
Stripping the wire just strips the listing away from the cable since internal conductors are seldom labelled.
