From what I've seen of mine so far, the breeder sourced, show quality, DCs very well fill the bill as a self-sustaining meatbird. While almost any DP breed will appear to be outgrowing them, picking them up will quickly tell you that quality Cornish are carrying far more meat than the DPs at almost any age. I also think your statement about poor meat-to-bone ratio is most probably dead wrong, though I have yet to processs any of my breeder sourced Cornish. I have, however, slow cooked many other breeds and seperated the bones from the meat; the amount of meat left was disappointing. It's true the Cornish have thicker bones, especially the leg shanks [necessary to support the bulky bodies], but poultry bones don't weigh much. I suspiscion the Cornish will actually surpass anything other than a CX in a meat-to-bone comparison.
I was surprised too at how big my birds were at slaughter (These were hatchery birds). They didn't look that big, but I guess it's the hard feathering that makes them look smaller than the big fluffy-puffies.
The Cornish cockerels I cooked had quite a bit of meat on them compared with the others.
The new Breeder (Murray McMurray

(Keeping the Ameraucanas, definitely)