I tried a breed a couple of years ago, called Bieldfelders, they are great birds, the eggs are medium, but they are a hardy breed and a pretty gentle bird. I've had Orps and Delawares, Austrolops, Turkens and I bought a few hens from a farmer I know called Sapphire Gems. Enormous eggs and a pretty hardy breed, it is a bluish gray Rock, so pretty and friendly. I love Speckled Sussex, but that breed is a bit soft when it comes to hardiness. If the new birds have a way to look at each other without reaching each other there will be less squabbles, but the older group has already set up their community, and you have to watch for fighting, and hens can fight as well as roosters with each other. I try to pick non broody breeds, because they have a huge fenced in area, 3/4 acre, to free range in, but sure enough the ones that want to go broody find places to get out and start clutches in the bushes, the gardens, etc, and that leaves them open to predators, in this area that would be racoons, skunks, and foxes. No worse sound than a hen being carried off into the woods in the middle of the night.