I am concerned that an unintended consequence of formal training and licensing of drones would be that serious, real pilots would avoid drones. Who would want to fly a drone and in doing so, endanger their commercial license? The Commercial License is much more important and valuable, so few pilots would put their license at risk while flying small scale commercial drones.

The result would be that lots of drones would be flown by less skilled amateurs.

While I don't disagree with the idea of training and licensing for drone pilots, I think it should also be "firewalled" from traditional pilot cerificates. Enforcement action because of a drone-incident should have no bearing on your rights as a commercial pilot.