Pjanic is unlikely - I don't see Roma selling him to their closest rival! Having said that, Pjanic is just the type of midfielder we need as he is fairly versatile and highly skilled.
Perhaps a really good mercato would involve minimal changes. Say 3 in and 3 out:
IN: Benatia (loan), Vrsaljko or other RB (10-15m), Pjanic (38m). PLUS Morata buy out 25m, and Lemina 9.5m = -82-87m
OUT: Caceres (0m), Cuadrado (end of loan), Pereyra (10-15m). PLUS Isla out for ~5m = +15-20m
NET = -67-72m. Forwards exactly the same.
CL squad for 1st half (22 players): Buffon, Neto? Lichsteiner, Vrsaljko?, Benatia, Barzagli, Bonucci, Chiellini, Rugani, Evra, Sandro, Khedira, Pogba, Pjanic?, Sturaro, Lemina, Hernanes, Asamoah, Dybala, Morata, Mandzukic, Zaza