Not a bad Idea. Be interested in seeing the replies.
Universal emergency battery disconnectThat switch looks good. I believe having a master disconnect is a really good safety idea. Just in case of an electrical fire caused by a shorted anything, especially a winch relay contact. I would imagine its very possible for the winch relay contacts to get welded together and your cant turn the darn thing off except to scramble to the battery compartment, find the tools to pull the post connector before the fire starts.