THE PLAN
I have thought at length about what to do with this wretch, and have decided I will drop a pickaxe in to him. He will construct a sub fort and will survive within it by himself. (or until more werechameleons are created.) From now on, his life will be lived within a den of his own creation, the only rule is that he may not breach the main fort. (I may break that rule for various reasons, such as creating a delivery room to dump his crafts into the main fort.)
Drawbridge airlocks are your friend.