I have no idea, but UEFA must surely have some rules on that too. Excluding young players won't make much of a difference here either since they normally are bought for lower fees and are on lower wages. My guess, and what I hope for, is that clubs have to exclude the players who have actually pushed the club over the limit regarding FFP. In City's case that would most likely be the last batch of players they bought; Negredo, Navas, Fernandinho, Jovetic and Demichelis. If that is not enough then I suppose UEFA would target the players with newly improved contracts, like Yaya Toure...
One can only hope that is the deal! If so, then I reckon a fair few players are likely to want out, and I can see quite a bit of turmoil at the clubs that have to do this. 🙂