As a starting point, I want to thank you for taking the time to put that together and to make 100% clear that I appreciate where you are coming from, and that is in the interest of providing fish with a good life. Too often in this hobby fish are seen as disposable, and not as real pets, but that is a topic for a different day.
Respectfully, I disagree with your assertion that people's beliefs about adaptability of tank raised fish to varying water conditions is "short sighted". There are certainly exceptions. Discus, rams, etc. that not only benefit from but require specific pH and hardness characteristics. No argument there, you (and more importantly your fish) are going to have a rough go if you try to keep discus in hard, basic water like I have here in upstate NY.
Other fish, to include severums and JDs, have proven much more adaptable. The oldest cichlid fossils are around 45 million years old, yes, but cichlids have proven adaptable not only on the geological time scale but also anthropogenic time scale. There are wild colonies of hobby cichlids from Hawaii to Florida, anywhere that's warm enough. I'd hazard to guess that mechanism for this rapid adaptability is selective breeding. We created a variety of conditions at commercial fish farm and in hobbyists' tanks over the last 40 plus years. That would have selected for fish that are more adaptable to different water conditions. Selective breeding is how we turned the basic dog into such a variety of breeds in only a few thousand years. It's a powerful force.
In my experience, for most fish in the pet trade, stable water conditions produces better results than chasing specific numbers. I respectfully disagree with the assertion that all fish require biotope setups matched to their native waters to thrive, which is the logical conclusion of what you are suggesting.
