I feel like there MUST be characters who aren't sufficiently associated with a currently-running title to have a "home office". I don't know, Machine Man? Paladin? There are plenty of characters even more obscure than them who've popped up sporadically and never had a home, and although it's unlikely that one of those characters would suddenly appear in both X-Men and Avengers, I'm sure you'd want to coordinate in case they do, right?