We are trying this with marans. We also have a few other single breeds. It's hard to keep numbers down and still have enough to cull properly. That , I think, is our biggest problem.
The man has decided not to breed for orps anymore. He loves them but we can travel a relatively short distance and get excellent breeder orp chicks reasonably. That means we don't have to separate and keep a pen just for orps.
The other thing is that in order to have pullets ready to lay when the older hens molt, you need to start them EARLY in the year and that means incubation rather than letting the broodies do the work. That means more time and space involved.
Roos are much easier to find than hens. We have no problems sending a roo to freezer camp if he no longer fits our breeding program. On the other hand, there is an Arcauna roo here for the 3rd year just because he is a nice guy and and excellent flock guardian. He will only go to a good home, if I can be enticed to give him up. I'm not personally attached to him, but any roo who sacrifices himself to a fox for his girls, has a home here and not a stew pot.
We have traded roos on occasion to get new blood into the lines.