So, under a hypothetical scenario of simply MAINTAINING the current squad: Lemina 9.5m, Cuadrado 22m, Morata 15-20m? (to cancel out buy back) = Close to 50m in fees and we are still down 1 defender (Caceres).
Benatia is a semi no-brainer if we can get him on a loan given Bayern's interest in Hummels. The buy out option would be the sticking point obviously.
Assuming we keep Cuadrado and Morata (HUGE Assumptions at this point), adding Gomes at say just 30m would take our net spend to EU80m already.
Zaza could be a source of funds (~25m possibly), but that is likely to be spend on Berardi perhaps. Money from Coman wouldn't arrive until the following year.
So potentially:
IN: BENATIA, GOMES, BERARDI........OUT: ZAZA, CACERES, One of Hernanes or Pereyra.
If we went for an attacking midfielder like Isco/Oscar in addition to Gomes, I think it is possible that both Pereyra and Hernanes could leave - trouble is the collective transfer fees for both would be 20-25m at best.
BOTTOM LINE: It is going to be an expensive mercato even if we don't do much. Having said that, last year our biggest expense was Dybala and we could have spent more (remember our pursuit for Gotze, Oscar, Draxler etc).