I don't think we'd buy D'Agostino so he could be Marchisio's back-up. It would cost a lot, probably close to a sum you already mentioned. Criscito would have a lot of job to do, don't know if he can do it. Motta would come out cheaper I think. We'll probably try to get him with Poulsen I guess. I'd probably buy one MC and rotate them so Tiago would be on his way out. My best would probably be
Buffon
Motta-Chiellini-Kjaer-Criscito
Melo-Mascherano-Sissoko
Diego-Jovetic
Dzeko
Of course Marchisio would have a big part there. Let's not forget injuries, all competitions and Sissoko's Africa's cup. If Mascherano is not available or too expensive I'd turn my back to him and sign Kacar.