Cornish cross are a hybrid and do not breed true. I have read many posts about people considering breeding them but most of the replies discourage it because of this. You could try keeping a couple of hens and a roo to see what happens. What have you got to lose? I'd clean the rest up, fatten them up a bit and process them. It's disgusting how those large commercial operations treat their birds. Even if you end up processing all of these chickens after you've doctored them up, they're still lucky to have spent their last days/weeks with you!!