If you are worried about worms and don't really have room for a large run, but want some of the benefits from keeping them on dirt, perhaps you should consider building as large cages as you have room for, and keeping them on sand? I'm not sure how well this will work with coturnix, you might...
It sounds like a really interesting project. I like your scientific approach to it. I'm not convinced it'll work, but I'd love to follow your progress and see whether the way you feed makes more healthy birds. At least, it sounds like your birds won't suffer in any way ^^
With regards to...