I would say, use those beautiful roosters and cross them over different hens. No telling what you may come up with and pull out the desired traits that work for you. You may have to cull/give away the undesirables, but keep moving forward.Th
Those are very nice looking birds.
Chickens are interesting critters with about 300 (?) breeds out there. There are books out there on genetics (I think I have a few), and serious and experimental breeders could come up with their ideal chicken, maybe not recognized by the APA, but something that would work well in your region. Of course, it's good to know the original background of the chickens you start with.