Kessie's a good player but I have my doubts about his ability to play next to Pogba. Very much a box to box player and seems to be advancing further up the pitch as he has grown older. Kamara (also out of contract in the summer), Tchouaméni, Brozovic (out of contract in summer), Fabian Ruiz, Caqueret, Ndidi and Rice would all be bigger priorities for me.
Haven't seen as much of him but Gabriel Menino from Palmeiras also seems to be very highly regarded and has looked very good in the few games I have seen. Obviously Brazilian league is a lower standard than the leagues the rest of these play in, but might not be a terrible shout even if just for added squad depth.