Don't want to stick my nose in but to state the bleedin' obvious United must get this appointment right if the DoF is to be part of the top decision makers at the club (if not, what's the point of the search process?).
If the main priority is to oversee transfers and contracts this is no job for an ex player with few contacts outside of those who handled his career.
The guys you are competing with have a network of top agents and club execs on speed dial. You really need to acquire those skills, preferably a guy that your rivals covet.
The alternative seems to be to get someone who is a populist choice but a big risk as far as efficiency is concerned.
The next round of appointments United make is crucial. Get them wrong and it may take a long time to recover.