Think a few of the lads have said already but the "Old Guard" of the likes of Smalling, Jones, Young etc. is quite scary. Not much to pass on to the younger lads not like you have had in the past with all the seasoned pro's we had to help nurture the young lads.
Koulibaly/Maguire would help with this, one of these would be the type of character who would lead by example and alongside Lindelof could form the foundations of a solid side barking out orders to people further up the pitch, hopefully with De Gea behind them, solid base to start from.
Matic I guess is still in and around the place so can help of the pitch, someone like Rice who has a bit of steel about him, great attitude and seems like the type of character we should be looking for.
I would also go for Neves who looks like a captain in the making, again great attitude great character and then obviously if Pogba stays he forms part of the 3 if he goes then replacement needed.
If Lukaku goes (which sounding like he might) we need (IMO) a very cleaver forward, even a false 9 similar to Firmino as if we go for a like for like replacement for Lukaku (say Cavani) we will have the same problems our the crosses from wide areas are absolutely woeful.
Dybala would be a dream signing for me, for that position, with Rashford on the left and Pepe/Brooks/Sancho on the right.
The less Lingard type clowns we have and the more Maguire type characters we can get through the door the better.
The above may well take two or three windows but heres hoping!