Honestly people bring up Arsenal as the blueprint but as a starter I'd look more towards what Newcastle did for a first window blueprint. They brought in Howe and then immediately raised the athletic levels of the side to ensure that above all else they'll be an absolute pain to deal with every match trying to run with them and win duels and 50/50 balls.
It's what I think is the single most obvious thing we lack in our entire side: Our spine has almost 0 athletic duel winners and runners. Varane and Martinez aren't really that, as one is a bit past his prime but a great box defender and the other is a world class aggressor and ball player CB but can struggle to defend large spaces in behind him (which is okay). Casemiro is 2 steps past his best now and it shows, Bruno is extremely slow and weak in duels, McTominay hardly runs these days and has never been particularly good in duels even at his "best", Mainoo is still a teenager but is arguably our best at this aspect right now which is sad. So I'd start this summer looking to bring in 2 physically dominant and athletic young CB's as well as 2 midfielders in that same mould. We aren't going to completely change the entire technical profile and style of the team in a single window, so instead we should look first to ensure that we are never bullied or outran in matches which will also help our overall defending and pressing structure. For example: Branthwaite, Diomande, Onana, and Thuram added to our squad and we immediately become far tougher to play against while each of those players possesses good technical ability as well so you aren't just buying a sprinter. Those 4 are just an example though, you can find plenty of targets in these threads that fit the bill but I do think it's the single most important "fixable" issue in the squad currently without us debating sales of Bruno/Rashford etc. or what forwards we need.
