Dybala and Mandzo are proven and reliable. Zaza proved to be a good backup, if he gets sold, we're prolly getting Gabi or some other forward. Pjaca won't be used in the middle. That's silly notion. He's most likely Morata replacement. His position on the pitch has always been more advanced, SS, LW/RW. Striker department is complete or at most need one backup, someone as a 5th striker.
Out of all these names only Pjanić is both reliable and starting material. Others fail the test. If we don't add more bodies here, experienced and free of injuries, we may very well end up with Pjanic, Lemina and Sturaro for the CL games, which looks putrid and far cry of last year's or even worse the year before midfield. I don't see how adding an expensive attacker solves this issue and it is entirely absurd to spend 94m on 28-29 yo. Think about it for a while.