I wasn't advising you to do anything, just suggesting there were other possibilities to think about. If you get chicks or growers, you would need to separate them until they were at POL, i.e. about 18+ weeks, but this could easily be done by dividing your run and giving them their own section. You could make a temporary box for them to roost in, they don't need perches or nestboxes, just a dry safe sheltered place. By the time they are several weeks old they could use an ordinary feeder and drinker, and its useful to have a spare anyway. They would need to eat growers pellets, another reason for keeping them separate, and also the older birds would attack them when they were little. For my two growers I used a small run on the grass during the day just for them, and catching and carrying them out in the morning and back at night got them used to being handled. I just enjoyed seeing them grow, and getting a bit more experience of raising younger birds, having previously bought pullets at POL. I think next time I need new birds I might get some growers of the Utility breeds they are currently breeding, as true to the original type as possible. By the time they are old enough to join the others in August- September the breeding season will be waning and integration will be easier than in Spring or Summer, especially if they have seen each other through the wire.
I may be wrong but I don't think Chalk Hill breed their own hybrids, like most places I think they buy them in at 16 weeks POL, but they are good birds and are kept on lovely big open grass paddocks whilst in their care. The two I have, a Columbian Blacktail and a Brown Leghorn, are very healthy and really good layers, so if you decide on POL hybrids that won't go broody, they would be OK. If you decide on POLs you would do best to keep them separate for at least a couple of weeks anyway, to settle in and to see that they are healthy.
Decisions, decisions - when like me, you can only keep a small flock!