How would you deal with the differing feed issue? Chick getting starter/grower and the other laying hens getting layer feed. Does it really matter much if the chicks get the extra calcium? Cost wise it would be the same $17/50lbs whether the 22% layer or the 18% starter.
To add, I have two roosters in the existing flock and I am not sure if that would make much difference with the chicks and integration much. Other than the roosters getting on the chick doing their thing ASAP haha. They are relentless. The other flock has been around them since birth separated by the wire you see in the photo. So they should be comfortable with them for the most part already.