You could raise them on very restricted feed from a young age, which stunts their growth and keeps them from getting too large. This is what the commercial raisers do for the breeding stock that produce the Cornish Cross chicks.
Yes, I agree.
The first "Cornish Cross" were a cross that included Cornish, but then producers started breeding both sets of parent stock in ways that produced better broilers. The pea comb is one of the traits they bred out. By now, yes the parent stock just look like Cornish Cross on a diet...
You could try copying what the original Cornish Cross were. Choose a hen breed that lays well, and grows quickly at a young age (New Hampshire, any color of Plymouth Rock, etc.) Cross them with a male that brings another trait you want (like purebred Cornish who have big breasts, but tend to...