I think it depends on what your needs are. I think you could easily breed for a meatier dual purpose bird like a Rock, or NH, Cornish, Buckeye, etc by focusing on that aspect of the breed. Then if you only need a few more eggs to keep your family fed why not just toss in a couple of hens that lay a different colored egg? Say all your meat hens lay a brown egg. Why not toss in a white egg layer? Would eat less, and crank out eggs. Their whole job of being there is to lay.
That way you know to incubate the brown eggs in the spring and any white eggs are to eat. No sense in incubating something that wont grow to what you want it to be. Or get EEs so you eat the blue or green eggs. Once you get enough birds hatched and on the ground then all the eggs go to eating. This would help keep your total number of birds down that you have to feed, and house cutting costs and you still get the production you need from both meat and eggs to keep up with your needs. Plus it increases the number of girls your roo would be able to chase and decrease the stress of continued breedings by your roo. So what if your meaty DP roo breeds your little egg machine? Your not hatching any of her eggs, so its really not an issue.
Granted if you have a steady market for eggs, sure sell them and expand to 2 flocks and keep a meat flock and a laying flock. I'm just trying to give you an alternative that might work for you.
I would think it would be pretty easy to replace an old layer(s) when her time was up. Offer something in trade to someone with a laying flock. Im sure you could work something out with someone locally. Would be worth a try. Maybe you keep an eye out at the feed stores and see if you couldn't pick up some layer chicks there. Or at an auction or talk to some of the 4H kids at the fair when that rolls around knowing that next year you need to replace laying hens see what they have available. Maybe they have the not as pretty/nice sister to the layer they brought with them to exhibit. Maybe they want to sell their layers. Hard to say but you'd have options if you start looking.