Lots of things are doable, but may not work in practice like they work in your head. It will be trial and error, every bird is different, every hen is different, every flock is different. Some hens will refuse a roo they don't like (which can result in injury), some roo's won't take no for an answer and will terrorize the hens, including serious injury. Especially a young roo or cockerel. A group of hens can sometimes hurt a roo badly also if they gang up on him. There are infinite variables. Probably the best working system is one with many enclosures, so that you can have separate groups to breed for the reasons you are looking for, take your prime purebreds and breed them in one, put your chosen mixes in another. Things would be calmer over all, they will form a flock and everyone will be more content. You can remove or switch out as you lose birds, add birds, or end up with a roo that is unacceptable for breeding for whatever reason. If you want to keep a lot of boys that aren't going to be used, put them in a dedicated bachelor pad as far from the others as possible, so that they don't (hopefully) fight. Every one of them is different. I have 3 roo's, two get along fine. One of those gets along with the third but the other does not and tries to kill him every chance he gets. So he is in his own pen with his own girls. One of the criteria I use in deciding what boys to keep is which of them the hens seem to like and tolerate more. I figure they know better than I do. Looks isn't everything. None of them are human aggressive.
