Clearly the issue of drones is complicated, and no single "solution" is going to solve potential conflicts. If I don't miss my guess, the solutions to the great majority of these issues will come about through pressure on manufacturers to install technical limits, be it "geo-fencing", soft-failure when comms are lost etc, combined with a licensing system for the larger drones.
A measure I'd like to see is manufacturers being compelled to "life" the software that controls them, that way periodic and unavoidable software updates could be used either to introduce new limits on their flight-envelope, or indeed could render a drone permamently grounded if it enters controlled airspace, for example.
Some back-and-forth telemetry would be helpful here so that a misused drone would effectively report itself for entering controlled airspace, identify the licensed owner and ground itself until the issue was resolved.
Currently, as far as drones are concerned, we're in a situation akin to that of commercial aviation in the 1920's and 30's, where technical advances were creating new problems at a faster rate than the legislators could deal with. Aircraft aviation survived and thrived despite this, and in turn we'll lean to live with drones as the legislation matures to contend with the them.
There is, no doubt a certain attrition-rate of drones in private/clueless hands, and so it's reasonable to suppose that within a short number of years the great majority of the currently umlimited drones will no longer be flyable.
The trick is going to be legislating without clobbering other spheres of UAV's- eg RC model flying, (which has an excellent safety record) as "collateral damage" in dealing with the muppets flying drones close to commercial traffic....