If I were running Everton I'd do the following:
Set up a structure which is Everton - this would encompass youth training, sports science, medicine, analytics, scouting, recruitment. This would be staffed by Evertonians with the best training/internships you can get so that best practice could be bought in from around the world.
When a new first team coach was appointed they would simply bring in themselves and 5-10 others who would deal with the first team. Training, tactics and motivation would be their remit.
My worry was that after Moyes left we lost a lot of infrastructure that he'd set up. Our old analytics department was regarded as the best in the business but they are now all at Man City. Some of the academy staff are now at United as are some of our scouts with one at Chelsea.
is.