Delawares and Dominiques were once choice meat birds. If you get breeder stock to start with, instead of hatchery birds, they both grow faster than standard Cornish. (please, note I said STANDARD Cornish, not Cornish X) And, If you use a Standard Cornish roo over just about any heavy breed hen, you'll get a decent table bird. Don't expect the extremely meatiness of the broilers crosses, but a good bird anyway. If you use hens of relatively fast maturing heavies, even better.
I butchered 4 roos that were Brahma roo over dark Cornish hen. That's bass-ackwards from what I know works better, i.e., C. roo over whatever breed hen, and they grew slowly, but they all dressed out to over 6 lbs., 2 were over 7 lbs, and the breasts were much meatier than ordinary dual purpose roos have been. And I have eaten a LOT of dual purp roos. They were not processed young, however. I hadn't fed them like broilers, and they grew slowly. Then, experimenting with feed blends, I upped the protein a lot, to about 20%, and they suddenly just about doubled in size in about 2 weeks. I was busy with other things and didn't butcher right away, though. I just did the 2nd two less than a week ago, they were probably about 5 months old. So they'll be crock pot birds, but meaty ones, instead of the scrawny crock pot roos I've had in the past.!