First up, I wouldn't count Bruno and Mount among our midfield options at all. We saw from January onwards what Bruno is capable of, when he plays in his natural position. Playing him deeper out of some injury necessity, will ultimately deprive us of our most productive attacking asset and that makes it not even worth considering in my mind. Mount is whatever; three full 90min in three years speaks for itself. Having him as a backup from the bench at times is a bonus, but nothing more.
In terms of who to buy, you go for the best you can get of course. For that deep midfield role it's Tchouameni, or perhaps Camavinga. If it's just physicality, ground coverage and speed you're looking for, you go for Baleba, or Scott. If all of these are priced prohibitively, then you consider Berge, or Kone. Garner should be an option too, or perhaps even someone like Scalvini, especially with the ability to potentially cover three positions.
But the only correct answer here is: I don't know. Because I'm not a scout and I don't have all the information necessary to make a call. I don't know the exact fees required, the wage demands, availability, or how far United's budget stretches with or without the credit facility. We're supposed to have the best-in-class people in charge of our transfer business and it's their job to make sure we don't leave ourselves short and risk falling out of the Champions League spots again. They were lucky last season that Carrick came in and did so well. You'd think, considering how important consistent CL qualification is for the club, they would do everything in their power to absolutely make sure and make it watertight that we can make it year in, year out from now on. Because that's the only way out of this malaise and back into the upper echelons of European football. Where this club belongs.