I may be wrong (it happens) but I thought that clubs that employ a Director of Football usually appoint a First-team Coach, rather than a manager, as a consequence. It is then the DoF's responsibly to address the shortcoming within the playing staff in terms of identifying transfer targets and dealing with contracts and departures, leaving the Coach to focus almost solely on preparing the side for matches, i.e. training, team selection, tactics and running the team from the dugout.
And therein lies the problem.
How many names currently in the frame are solely coaches as opposed to managers? As others have said previously, why would anybody with anything approaching the skillset we desperately require to sort out this ragtag bunch want to come here only for Les Ferdinand to be hanging about like Banquo's ghost telling 'em who they need to buy, who should be sold and who should be the first name on the team sheet each week.
I'm struggling to think of anywhere in England where the DoF role has been an undisputed success. I guess there must be examples, but those are probably at clubs where the individual occupying the DoF seat has been very low profile and hasn't needed to be publicly recognised.