I do this on a somewhat larger scale (35 layers in our flock, with 4 roos, and just raised 24 Cornish to slaughter age, and have ordered 40 more.) and I can tell you first hand NO, you will NOT want them mixed.
First reason, sanitation as stated already. Meat chickens are eating, drinking, POOPING machines. Thats it. And they dont poo like normal chickens do. Its like a Playdoh squirt gun when they poo and SMELLY. They lay in it or even roll in it sometimes, and I personally would just never expose my layers to that mess. Just not good for them IMO. You'd be exposing your laying flock to all sorts of bacteria breeding conditions and all sorts of other "ickies". Plus, do you plan to sell or eat your layers eggs? I would NOT personally want to eat eggs gathered from a coop with meat chickens! Bleh!
As far as good laying breeds, you have several already. RIRs, Buff Orps, and Barred Rocks are all great layers. If you want a good production type white layer go for a brown or white leghorn (both lay white eggs) or similar breed (some hatcheries call them something else, but they are essentially the same bird). They lay TONS of eggs, but I've heard they are often flighty and skittish too.
Second reason to take into consideration thats yet to be mentioned, what about forming attachments? If you love your layers and spend hours a day with them, but then raise your meat chickens with them as well, wouldn't you then become attached to the meat birds, thus making your job in the 'end' MUCH harder to do? When raising birds (or any animal) for meat, it is FAR easier in the long run to stay distant from them (ask anyone here) or you'll end up either crying your eyes out on slaughter day, or worse, keeping them because you just cant bare to do what needs to be done.
I keep our meat birds in a whole seperate area of our barn, where I go only to feed and water them and check that they are comfortable (fans, clean bedding, ect). I do not talk to them, or hold them (other than close to slaughter to get weights), and therefore, I have no emotional attachment to them. I'm not cruel or inhumane with them, I just draw a line that I am careful not to cross and get too close to them. That may sound harsh to some, but it is how I detatch myself, and in the long run it is still a far better exsistance for them under MY care than in some factory farm somewhere. I adore my layers, and often spend hours just in the yard with them, or sitting in the coop with them. I just cant even fathom how I would emotionally withdraw myself from the meat birds if they were always there, too (in the yard and coop with the layers.) But that might just be me.
. Probably won't need as much with the ten layers though. The meat birds lay around and need thick bedding, plus they poop ALOT! I had more trouble with them in the brooder, as the litter had to be changed often to keep it dry. The litter in the coop has kept dry and the laying hens seem to congragate at night in one corner so I put down fresh bedding there first. I do also stir up the bedding daily. I do have perches , but the laying hens like to huddle, I think babies just like to snuggle together for comfort, but they do perch in their run, they just might be afraid of the dark yet? The meat birds don't snuggle or perch, but when it was colder at night the hens snuggled next to the meat birds for warmth instead of going under the heat lamp, so they do serve that purpose well. 
