ootai, I got that 20:1 ratio from a UK website... I guess everywhere is different.
What worries me about your strategy is that you're using warren hens for meat production. These warren hens have been bred for centuries to put all their energy into egg production at the expense of putting on weight. In the commercial world, when these guys' egg production drops off they get tuned into soup, stock and pet food, they're not the chickens you roast on a Sunday. In Thailand the meat chickens are white, you see them in cages on the lorries, but I have no idea what breed they are.
Out of around 40 chickens we get between 10 and 16 eggs a day. We have a lot of retirees who are having an easy old age. They do bully the newcomers a bit but the cockerel soon sorts out any real nastiness. There is a pecking order of course but that's only natural and you have to let them sort it out.
I think you should use these hens for egg production. I think an egg sells for around 5 Baht... I just think using chickens bred for egg laying efficiency for meat production is counter productive.