The way I read this you are talking about getting some dual purpose cockerels and using them for stock. You want to know what you can do with the meat after you make stock.
When the hormones hit a cockerel during adolescence they have an effect on the meat. The meat develops a "gamey" taste. Some of us like that, some don't. The meat also develops texture. That texture is why age makes a big difference in how you can cook them. Some cockerels may start puberty as young as 3 months, some may wait until 5 months or so. They all vary. Females also develop more flavor and texture as they age but it's a lot slower.
Since you are using the Cornish X broilers for meat, I'll mostly stick to using these cockerels for stock. When I butcher my old hens and old roosters I cut them into serving pieces, mainly to reduce the volume. I pretty much save the entire carcass, neck, back, gizzard, heart, and feet in addition to the regular wings, breasts, thighs, and drumsticks. Yeah, I know where the feet have been. After rinsing well I dump the feet in boiling water for about 15 seconds then cool them. If you overcook them they are a pain to peel but if you get it right the claws and spurs twist out and the skin comes right off. It takes some practice. If I am using them for broth only I do not age the carcasses but freeze them immediately.
There are different ways to make broth or stock. You may already have your own way. I use a large crock pot and put a dozen peppercorns, a bay leaf, chunks of celery, carrot, onion, and garlic, and some herbs like oregano, basil, maybe parsley or thyme. Maybe leeks or chives, whatever I have in the garden. Suit yourself. I put enough chicken in there to pretty much fill the pot but so i can still cover with water. Then I cook that overnight on low, maybe 14 to 20 hours. After it is done I strain out the chunks, de-fat the liquid, and strain it through cheesecloth. The broth is done.
Now for the tedious part but what I think you are after, I go through those chunks and pick out the meat. There are some small bones so be careful. That is fully cooked well-flavored chicken meat. That is good for chicken tacos, chicken salads, soups, or stews. I often make a sandwich for lunch with that meat.
Since it is fully cooked I would not expect it to make a good sausage. To make sausage I'd think you would need to de-bone the meat raw, age it, and grind it pretty fine. Even then you might have texture issues but maybe not. I have not tried it. I don't know why it would not make a good sausage if you get the right mix of herbs, spices, and fat. You can make sausage out of alligator, venison, bison, or turkey.
My main suggestion is to try it, see what works for you. We all have our own personal preference, tastes, and preferred textures. What works for me might not work for you.
When i butcher my dual purpose meat chickens, in your case the Cornish X, I save the back, neck, etc. for broth. I don't just use my older birds. When I cook the chicken for the table, I save the bones in the freezer. They are going to be cooked enough later that they will be sanitized. Some people use these for broth but when I get a gallon bag full I put them in the crock pot covered with water overnight and save the liquid. If I have it, that liquid is what I use for broth instead of plain water. I squeeze all I can out of my chickens, very little goes to waste.
