This gets asked an awful lot... so this is the brief answer, search this forum to see posts by people who actually do this:
1) Homebred broilers can be done, they just aren't as optimal, fast growing or efficient as commercial day olds.
2) All broilers are hybrids. So if you hold back broilers and rebreed them, you are re-breeding hybrid birds which means within each clutch of 100 eggs, you'll get 100 different results. It's not entirely predictable.
3) My best results were rebreeding hybrid broiler hens to a Dark Cornish terminal sire. They were heavier than any purbred I've ever hatched, yet they were a couple/few weeks behind even my Freedom Rangers.
It's something fun to do, but keeping a 'breeding flock' of meat birds to cull when you need them really isn't practical. The feeding and management is different, leaving you with split flocks and double the work. It's best to raise broilers as "crops" then harvesting them to the freezer.