Don't let him have any say in transfer matters if he want to sign Memphis as a starter and play him as the #9 and Wijnaldum for the same reason in the midfield
I mean on paper every combination with Depay on the left (or CF) and two out of Messi/Fati/Dembele looks better than Griezmann in there. But I get your reservations. Before the season I thought we should make a ton of changes, but now I am perfectly fine with our midfield and defense (+Garcia or similar). I definitely think our attack needs the "most" changes, but its really hard to say what exactly we should do.
Depay is okay, but far from a big improvement, and if Griezmann stays (I am 50/50 on this) he may not make too much sense. The latter is a worse fit, but individually superior.
A worldclass CF would be great, but there are only two somewhat available options (Haaland and Kane), and they are still highly improbable (not that I would like Kane in particular here+Levy is a pain in the ass). Haaland would be incredibly expensive as well+Watzke is a pain in the ass ;-)
As an irresponsible fan I would say f*ck it and try to poach Moukoko for CF - take a page out of Florentinos playbook and open the Kindergarten. Not much other talent around I am afraid (Malen is far from impressive and I have no idea about Daka, maybe someone can say something about him).