Thank you all for the helpful advice!
@dc3085, it's very interesting that the chickens are much more likely to make the quail sick, rather than vice versa... I think that this must be one of the reasons that @GD91 has had a lot of success with raising quail by her chickens (as they are elevated so the chickens are exposed to the quail, but the quail are not regularly exposed to the chickens... brilliant)!
Based on the quail requiring a smaller space than what I had imagined, I would certainly opt to keep them separate from the chicken coop, for my own backyard setup.
So long as I am legally allowed to have at least 2, I am definitely NOT giving up on getting my chickens just yet. Having quite a few neighbors with definitely more than two chickens, roosters, peacocks, etc. in their yard... I'm starting to hear ya on the "screw the law" bit, lol. In my ideal world, I'd have at least 4-6 hens to start.
I know this sounds like a rather unconventional statement, but I'm not particularly concerned with predators or coop design right now. I live in Hawaii so the only predators we have are rats (and maybe mongoose?). My backyard feels like a pretty standard size for the suburbs and I think it can definitely handle a pretty good size coop with an attached, enclosed run (I already drew out the plans to blueprint in AutoCAD). I plan on building my coop and run out of mostly wood and hardware mesh. I'm going to give the coop a green roof with lavender, marigold, and yarrow to attempt to deter pests. We're directly across the street from the beach, so I'll be using a mix of sandy soil as the ground for the run, and just pure (untreated) sand for the coop. The coop and run are going under a mango tree and they'll be getting fed strictly organic through various plantings and raised grazing frames throughout the run (will occasionally supplement with organic feed). As I noted in my initial posting, I'm surrounded mostly by agricultural (farm) land; probably pretty far from "city-folk" at this point... that said, checking out a vent still grosses me out a little bit, haha!
Our entire family is vegetarian, so we're only looking at the chickens for egg laying (and because they're awesome). We already have people who will take them once they're done laying, though. Also, I'm stay at home, full-time, so I'm ready and willing to put in the necessary efforts. The idea of having quail is so very cool and I think truly a homesteading must! I'm convinced that I need to give myself even more work by having both chickens and quail (in separate coops, it seems)!