I think that is a very fine line you have to tread. You want the coach to be comfortable with the player but coach cycles are short and their outlook is always short-term. You will buy a lot of players on past performances and you'll open yourself up to Zaniolo/Radja deals.
Our transfer policy has always been fine, if not good. We went from Pepe to Ronaldo. We started with a paper clip and bought a house.
Oh its definitely a fine line, you always need to look to the future with signings, and we have come a long way, with some excellent signings, but i'm not talking about specific players, but Managers should defiantly have a say in the 'types' of players that are signed, ofc if a market opportunity arises you take it.
but none of us know how it works, or what input the coach has in the signings here, but i'm just talking hypothetically based on rumors.