GK: Neto is perfect as backup, but IF he wants to leave, signing another backup gk shouldn't be a problem. Can be a potential Gigi replacement (Meret or whoever else), who'd learn from Gigi, become acclimated with the team, and let us evaluate him for a yr....or just sign your avg backup.
Defense: Think signing benatia is just a formality with Bayern. Only thing missing is a third option for lb.
CM: This player needs to be content with competition for places, needs to have physical qualities that khedira/pjanic/marchisio don't, needs to be able to play as AM, and has to be good in the air. We're always poor at defending set pieces for 1-2 months every season (since Conte's time) before it gets fixed. If you remove Mandzukic and Khedira from the lineup, we'll have that problem. Plus, with pjanic's deliveries we need to maximize scoring from set pieces.
Attack:. Right now, in terms of the characteristics of the players, it's the perfect combo with a CF who contributes defensively and can show to the ball and switch play, playmaker (dybala), hardworking winger who scores a few goals (Mandzukic), and a dribbler who can take players on (Cuadrado). Quality-wise, need to improve on Cuadra. Need someone with his speed and dribbling but someone with consistency and DA's crossing and final balls. The others, including Mandzukic, are untouchable.
And a backup for Mandzukic. One of these two players needs to be able to play as striker.
If spinazzola is good enough, he can be the reserve for all the flank positions: 3rd choice lb/rb, lw/rw, lwb. Alternatively, sign de sciglio.
Sign Meret, Schick, and other players with potential and loan them out along with bentancur.