If Mascherano wants to come, we should make space for him, if it means he gets Gigli's parking spot. Mascherano is someone we can build the team around for the next...I don't know 6 - 8 years! He is worth every penny, as he would be our answer to Pirlo. Any upright mammal can be told to just destroy in the midfield next to him if we needed such player. Nocerino (it is obvious now) needs more time. Marchisio will probably not be "that much of an upgrade" (I know that's blasphemy here, but think about it), and we need results now... So that leaves us Zanetti, who will not be around for ever, and its a miracle he's still even effective, and Sissoko, who can work fine defensively for us for a year, but then we can sell him like that because he is young. On the other hand if he is our Rino-Gattuso-like destroyer with Pirlo-like Mascherano, so be it. If he develops, great.
But Mascherano should definitely be made a priority (I know we have other needs, but we need to build ground up).