No, not looking to stir things up. I'm into commercial (read: efficient) agriculture...
You really can't compare a commercial operation to a backyard operation as far as efficiency. A commercial operation, wether it be chickens or cattle, has THOUSANDS of animals they are using to make a profit. Because of the sheer numbers of animals, they can absorb a certain percentage of loss (i.e. deaths, culling, low production animal) without a huge impact on their income. They also have the ability to freely cull any animal that is not producing up to standards.
As a backyard operation, with a few dozen hens (or less), you CANNOT absord the same percentage of loss without cutting into your profits. If you cull a layer because she is not laying, you will need to replace her. So you can pony up the cash for a local market price of a young laying hen, or you can invest (and lose) time and money to raise a chick to replace her. Meanwhile, you are losing profits in the form of eggs not being laid each day. Get it? Same thing applies if you have poor living conditions for your layers and they get ill due to stress, and die.
You would be much better off investing your money into building housing for your flock that encourages longevity, health and high laying. You'd get a much better return.
And I would suggest talking to a local extension agent about your theory of a few hens free ranging on your sheep pastures increasing the copper to a toxic level. I've never, ever heard that before. I'm sure it could be a factor if you had a few hundred birds on an acre or so, but I cannot fathom how it is logistically possible with less.