The problem with getting rid of groundbased NAVAIDs is that it invites terrorism...practically begs for it.

Ground-based systems have outputs measured in tens of watts. In order to jam that you would need a powerful transmitter, something that would be hard to make mobile.

GPS satellites might output 500W but by the time it reaches the aircraft near the ground it has attenuated to milli-watts. One jammer in a mini-van could probably degrade GPS enough to shut down all approaches in a large metro area...say Los Angles.