That is more or less how it's supposed to work now (the original idea behind disease property). Alternatively one could add a mix of bonus and penalty for too low diseases as well like "obsessive cleanliness" that give positive health at the cost of other things like negative happiness, less productivity or something. I think this might be annoying as one has to keep an even tighter watch on property values.Actually maintaining that 0 limit but purposely no giving enough way to fight diseases/crime as you pop growth would also be quite interesting. As your pop grows, you get more and more diseases until city growth is stopped altogether. Then, with tech advance, you become better at fighting disease and your city can grow a bit more. City size would then mostly depend on its food resources and disease-fighting buildings instead of maintaining a near-permanent advance for cities founded early on.