The role he takes has been deployed for years in hockey, in the national premier league in the 80s it was referred to as ‘ghost back’ for years it confused the hell out of opposition teams, even when they expected it they didn’t quite know how to deal with it OR how to take advantage.
It actually started out with a ghost wing, dropping the extra body to create two CHs one offensive and one defensive but the ghost back seemed to work a lot better to overload the midfield when needed. One thing I will say is that you need the rest of your defence to simply be the best, any second rate players and your dead in water, which we do have as city !