Really think folks are looking at this the wrong way. Harry Maguire will be at Manchester United next season, and on one of the larger wages. He will be a big part of the first team. So, ETH needs to work out what to do with him, rather than plan without him.
For me, the big change from actually really good Maguire (we had an impressive defence just 2 seasons ago built around him) to this season is composure. He's just totally lost it. My big hope at the start of the season was that having an incredibly experienced, trophy-laden Varane next to him would let Maguire take second fiddle, and listen and calm the f*ck down. Instead, all I hear is that Varane has never been vocal, so Maguire seems to have gotten worse.
A better man-manager (and let's be honest, Rangnick doesn't appear to do that at all) would have tried to fix Maguire's psychology. Hopefully that's something ETH can work on.
If Harry can calm down, keep things simple and get back to his usual game he's still a pretty solid premier league centre back. There is no reason a combo of Maguire/Varane shouldn't be very effective - both are good in the air, one has speed the other is pretty rugged. If I were ETH I'd be aiming to work with that, and any player that comes in will replace Lindelof in the pecking order, or make up numbers with Jones/Bailly likely off.