For eggs and meat, as gpop said, coturnix are the best. For brooding their own young, as far as I know, buttons are best. But the live weight of a button is around 40 grams and their eggs are tiny - they aren't worth much as a meat and egg supply. Very rarely, a coturnix will brood its own young - you'd probably be better of giving up on the idea of them brooding their own young and just purchase an incubator and make a brooder if you want quail.
Keep in mind when modifying the coop, that quail have a tendency to boink straight into the roof of their enclosure when scared - and they can do this with enough force to kill or seriously injure themselves. To avoid this, you could for instance pad the roof of the hutch part with foam rubber and apply bird netting or similar soft mesh a couple of inches below the top wire in the outside part. Quail are also pretty bad at seeking shelter from rain though, so you might want to put a roof on the outside part a well.
And, as gpop pointed out, chicken can carry diseases that quail are very susceptible to, so clean it well. And even the smallest predator poses a threat to quail, so hardware cloth all over the place will help you keep them safe.