So chickens and quail aren't a good mix in the backyard

To be blunt but not belligerent, you have read the cons, warnings, dangers and reason not to do this. So why do you persist on trying to find someone that will tell you it is okay? I will not do that.

But I will say it happens (birds eating and feeding in other species crap, fecal, and digested foods) Yum!

I too am stubborn when trying to make something work, but in saying that, I heed to warnings and work around the cons and find different routes and solutions. The reason for that is simple, the last thing I want to do is potentially increase my burdens and decrease my flocks due to diseases by creating such opportunity and scenarios.

If your whole focus of concept is based on "A no waste of feed" scenario, I would look to a different method of feeding the quail in the pen so that the feed does not hit the ground and attract the chickens, mice, and other wildlife that might feed on the left overs.

By the same tokens, you state the chickens have a free range of 2 acres, so in that light I cant see the logic to calling them in or allowing them to eat from the voids of crap and potentially spreading any airborne type infections upwards to your caged birds or outwards. If either do catch a disease they will be spreading what they contract (either) into the open ranges of the wild, or inwards toward the caged birds. So again, why create those situations?

Wildlife is responsible for a range of disease and I am sure you don't want wildlife bringing in diseases (such as the avian flu) to your flocks, so in that same light....do you want to promote the outward spread diseases into the wild either.

I am not saying either will happen, but there is that strong potentials...My point is simple, find a better way and different approach and your flocks will be much healthier. Having a variety of stock is a two ways street, you are not only preventing diseases, you are avoiding the potential of spread of disease.