Premise:
Most of security tends to cut off the cling heads first chance they have. Some even carry circular saws with them, in case the occasion presents itself.
Its a fast and easy way to definitely kill a changeling, cancelling their power to revive themselves and is sometimes seen as a dirty, un-fun move.
Proposition:
A passive ability that activates when a changeling head is cut off. The head grows disgusting tentacles and is able to vent crawl. Same as head slug but without