If we are gonna keep playing with a 4-2-3-1 and bet all in on that. We should go all in for Sanchez, it doesn´t matter if we don´t get anyone else (except freebie Kolasinac)
That move would solve a lot of problems, atm we don't have a striker on the bench when playing 4231, but getting Sánchez and playing him LW would make Mandzukic sit on the bench, perfect substitute for Higuaín. Moving to a 2-man midfield would make our shortage of quality midfielders less of a problem.
We could do with Pjanic, Marchisio, Khedira and maybe Sturaro, not to mention Lemina, Rincon and Asamoah(?) would still be here.
It would also give Pjaca more time to play considering he would be the next option on the peeking order for wingers.
We would still probably need some buys like an AM that could substitute Dybala (maybe Pjanic could double as it), another winger... but aside from that, the team is basically done and extremely powerful