[jcrawfordor]

For what it's worth, in any urban area, the 1000 feet above highest object within 2000 feet horizontally is much more likely to apply. While the actual regulations are somewhat loose on definitions, most pilots I know would describe the "500 feet from anything" fallback regulation as being applicable only when there are no structures or other populated places nearby.

In any case, raising floor altitude for non-RC/unmanned aircraft to 2k feet would pose fairly substantial challenges as, even ignoring the fact that airports require approaches below 2k feet and are often near populated areas, lots of commercial applications for light aircraft require low altitudes. Survey, photography, news gathering, law enforcement, sightseeing, etc. These are many of the same applications drones are posed for... there doesn't really seem to be any way to simply separate these types of traffic entirely.