I think DoF works great when you buy the very best players in the world. Its a no brainer. Director of Football buys Ronaldo, Bale, James, Modric, Benzema ... I could go on. Then the teams swaps and changes the manager, whose style of play might alter a little, but it matters not because the best players just go out and beat other teams.
But wait, even at Madrid, where the coach is changed every two years, and the President buys players like billionaires buy new Bentley's, just 'coz, the team can underperform, fail and have to reset.
I am a traditionalist. The manager knows how he wants to play the game, and provided he has a chief scout who he cna clearly communicate this too, between the two of them targets are found and then the clubs secretary, chairmen or whatever the fuck that motor bike riding dick wants to call himself, gets the job done.
The only real argument should come in when the managers desire for a player outstrips the clubs willingness to make the fee/wages. The likes of Ian Ayre should simply be helping Brendan get the players he wants, within the clubs financial constraints. He should never be picking targets.
A director of football? That means we will have two people thinking about the type of player that suits us, and the DoF will be thinking about whether a player will fit in if the current manager gets fired - a variable that is not going to be all that helpful.