If you use deep litter, it all gets broken down like in the forest floor, and the birds stay healthy. You can look around on this forum, lots of people have happy, perfectly healthy quail on the ground.
With a little adjustments you can have both raised cages and deep litter. Im doing that .
Right now i have a trio in an outside pen it is a prefab rabbit hutch from
tsc, two stories tall, with a ramp, but working on making the ground deep litter, its just starting with an inch of sand and some straw. The top layer is wood slats for the floor and a sandbox. They are slowly figuring out the ramp... they definitely prefer the ground even though it is all 4 wire sides and so rather exposed, the top they feel more secure in, with only aquarter of it being wired, but like to play on the ground...
and my other trio is in a super large grey tote i replaced part of the widest side with hardwire cloth, and inside is up to 5 inches deep litter. Every 3 to 5 months i toss it out and start again with one inch of sand with 1 cup of sand added twice a week or more. This works pretty good in the tub but the quail have decided the best thing to torment me with is to knock their water over, flood the land and make me clean out and start over! So the wire is easier for me and less stinky, but they do seem alot happier with a full ground of sand... someday i would like a larger ground pen deep litter so they can have the best of all worlds! My quail friend keeps his on just wire with just small dishes of sand.
Daniel, you say tractors would be your first choice if you could do it, well my first choice if i could do it, would be to predator proof wire several acres of land all around my house here on our farm and let my quail live in a giant natural aviary!! maybe the front yard for my chickens and the back yard for my quail

ah my dream farm! But meanwhile im stuck with tons of hutches and a few coops, because we have so very many predators my chickens can't roam free. Our peacocks and turkeys that roam free get thinned out pretty often im afraid! (Sorry for the tangents)