I originally chose Golden laced wyandottes and added some silver laced wyandottes with one barred rock. They were suppose to be friendly but they were not - the barred rock was. I ordered a variety pack the next year and I got some great chickens. I went to a chicken show and learned a lot too. I found an old photo of my grandmother and her dominiques and I ordered some. I really love cream leg bars. I had a breeding pair but lost them both last summer. Next spring I am ordering new stock - a roo and 2 pullets. I live on 5 acres so I have room to do it but my chicken run is only about 1000 square feet.
The thing is...stuff happens. Attrition happens, predators happen. If there is a certain kind of chicken you really want and you have room now or eventually, you can get it.
I think you should enjoy and learn from the chickens you have now. Maybe you start a separate flock with a special breed and start with a rooster and 3 pullets.
You can let them flock together or not. I have found that chickens that are not raised together will not flock together or if they have a choice of coops will coop with their flock mates not intermingle.
Hope that helps
Caroline
I think the Dominique would be a good breed to raise. They are called "America's first breed" and on The Livestock Conservancy's watch list. Plus, your grandmother raised Dominiques.
How many of them do you have now? Do you plan to breed them, or did you just want to have some?