People won't be keen but apparently Wanyama only has a year left on his contract.
I'd get him in in a heart beat. A proper #6, and under him and Mourinho we could play him and Morgan in tough away games and be ridiculously solid in the middle.
I think he'd be a great signing, would really toughen us up and free up Schneiderlin to play a bit more of a dynamic role, the role that he is more accustomed to. However, I think I would generally want to play Blind at centre back behind that midfield partnership, as we would need that ball playing ability to play through the lines and remove any creative burden from the midfield two (obviously you would probably want to drop Blind against a powerful forward, Carroll, Benteke etc).
We have to be looking to replace Carrick's ability eventually, but I feel that we may have to wait until we have CL football to find a worthy replacement (and it's a role that we can do without, or keep Carrick for another year).
We certainly need a pacey and tricky right winger, I would look at Mane as a realistic priority here.
Then we need to add goals. The emergence of Rashford has lessened the need for any kind of back up player, so we need to replace Rooney's goals, or more realistically, supplement them, as we know he's unlikely to find himself on the periphery of the team. The option then, is to find a new starting striker and play Rooney at #10, or play Rooney at #9 and find a goalscoring #10. My preference would be the latter, as James is seemingly available and I just love watching the guy play. He can also play wide right, which is a great bonus should we need to revert to a 4-3-3.
The emergence of Rashford and Fosu Mensah have really been a positive this season, and I'd hate to see their paths blocked at this stage. I'd also hope that Depay can come good under the correct guidance and a more attack minded coach. Let's hope so.
I'd move Rojo and Mata on if possible, so in terms of squad coverage, we'd have:
Goalkeeper - De Gea / Romero / Johnstone
Left Full Back - Shaw / Darmian / Borthwick-Jackson / Blind
Right Full Back - Valencia / Darmian / Varela / Fosu-Mensah
Centre Back - Blind / Smalling /
? / Fosu-Mensah / Jones / McNair
Holding Midfielder -
Wanyama / Fosu-Mensah / Blind / Carrick
Central Midfielder - Schneiderlin / Schweinsteiger / Fellaini / Herrera
Attacking Midfielder -
James / Rooney / Mane / Pereira / Herrera / Fellaini / Januzaj
Left Winger - Martial / Depay / Lingard / Mane / Januzaj
Right Winger -
Mane / James / Lingard / Januzaj
Striker - Rooney / Rashford / Martial / Depay
This squad has a lot of variation, a lot of pace in attack, and a lot more of a goal threat. I would look to phase out Carrick and Schweinsteiger next season and hopefully, with the carrot of CL football, entice a real ball playing midfielder that can dictate games in the way that Modric/Kroos etc can.
EDIT: I wouldn't pass up the chance to buy Ibrahimovic, mind.