What are the benefits to a mixed flock? I would like to hatch naturally, little to no intervention. I have raised meat kings and I don't want to go that route for meat, so a dual purpose bird is what I would like. I was given a huge black australorp roo and it was so mean and aggressive that I was afraid of the kids around it. It attacked me on numerous occasions just because I walked past it. Are different breeds of 'lorps more docile?
Mixed flocks are great if you are not planning on showing your birds! As far as egg layers, diversify your flock with several breeds such as Leghorns, Rhode Island Reds, Cochins, Barred Rocks... There is no reason to stick with just one breed unless you plan on showing.
As far as meat birds, the best option is a Cornish/Leghorn cross. They really beef up nicely on whatever you feed them! The one downside to this excellent meat bird, is that it can be difficult to breed them yourself. It takes a lot of planning, and attention to detail to build this kind of flock. My family would buy a hundred of these Cornish/Leghorn cross chicks at a time, raise them on organic corn. This flock fed our family of fourteen for a few months.
In my experience, large roosters tend to be pretty mean, and unfortunately unless they are cooped by themselves they will severely beat up on the hens, and the owners! I used to breed Rhode Island Red's for show and once my roosters got mean I cooped them in a separate pen. When one of my hens got broody I would let him in the main coop for awhile, collecting all the other hens eggs and giving them to the broody one. This worked pretty well, but of course different breeds do different things!
One note on my roosters is that they rarely attacked my dad, or once I was older and taller, me. We figured out that our roosters attacked kids, and my mom but only when she was wearing a skirt! Something about the shorter kids and the flowing clothing made him mad.