Honestly, i don't see the issue. Just give the word to any new recruit to blacklist him. Problem solved. It's a minor annoyance. The training dummy thing is a bit sad, i admit. Then, as others have said, treat it like a pet for your fc. He can't bother you anymore, he can just run around, so just treat it like you would a wandering pet. Either he will get bored, or he won't, doesn't matter.