I think there is a role for a DoF, in theory it makes perfect sense. You don’t want to keep emptying the knowledge bank every time you change your managerial appointment and he takes all his staff with him.
You need some continuity to gel everything together in the modern game.
The key is finding a good, experienced guy with the people skills to work with a variety of manager’s from probably a variety of cultures. He also needs the trust and backing of the board.