Borussia MGDB looks well coached whenever I see them play and Plea and Thuram developed nicely which bodes well for Rashford, Greenwood, Martial and Diallo. Also he might bring Neuhaus and he looks like a lovely fit as the partner for Fred in a pivot or with VDB against weaker teams.
Looking at how Southampton play, if Hasshenhuttl ran the same system here:
------------Rashford------Greenwood------- (Cavani, Martial)
----Bruno-------------------------------RAM------ (Diallo, James)
-------------VDB/Fred-----#6------------------ - (VDB/Fred, McTominay, Garner)
Telles------------------------------------------RB (Wan-Bissaka, Williams, Shaw or Alvaro)
--------------LCB-------Maguire----------------- (Lindelof, Tuanzebe, Mengi)
-----------------Henderson----------------------- (Backup Keeper)
would be my expectation of what he'd want. Similar to what we need anyways, but maybe we buy a left-footed #10 type like Mata as an alternative option to Diallo, unless he just wants to buy Ward-Prowse (the only Southampton player who makes sense for us to have come with him) or another #8 and have Van De Beek in that role. My guess is he'd want a technically stronger alternative to Wan-Bissaka and would maybe show affinity for Henderson because of his passing potential compared to De Gea, but he'd probably be fine with having both around and letting them fight it out.
Feels like this would work. We have younger strikers who don't have the skills/strength/experience to play alone, Bruno is not dissimilar to a Stuart Armstrong type while obviously being much much better and guys like VDB, Fred, James, McTominay and Williams (rumoured to be wanted by Southampton) all seem like they'd take well to high pressing. Not sure it's a good fit for Wan-Bissaka based on their fullbacks and the need to provide a wide threat, but he needs to improve that anyways unless we end up using him as Kyle Walker type 3rd CB/RB/RCB/RCM Pep favoured hybrid - or Mourinho style sit back while the other fullback goes hog wild - with Diallo, James or Pellistri wider out right and Diallo is the favourite for that job and will wanna cut in anyways so we're back to needing crossing and width from the spot.