Signing Cesç is an extravagance done for sentimental reasons only. He'll never take over for Iniesta or Xavi. When Xavi's down (like now) I want to see young Thiago on the pitch. He's the next Xavi - best in the world. Cesç better not take away any playing time from Thiago.
The best option is to play him somewhere else. Look at this link for some possibilities:
http://bleacherreport.com/articles/748020-fc-barcelona-where-will-cesc-fbregas-fit-in-bara-4-possible-starting-xis/page/5 . This analysis doesn't even show Thiago or the other new arrival, Alexis Sanchez who is expected to start. Sanchez is a great dribbler with amazing speed, but he has to discipline himself to play the Barça style or he'll become a detriment.
Money would have been better spent beefing up the thinning back line. When will Capitan Carles get healthy again? And how long can he stay healthy? That's Barça's biggest vulnerability, IMO.