I'm sorry but I doubt that there will ever be a system where by ATC could have direct control. It's too open to interception or control via the wrong party. Worse would be a scenario where the UAV is deliberatly flown into the target through third party interception of control.
How do ATC handle a scenario where the pilots of a manned aircraft are incapacitated? They don't have any way of gaining control.
Look at
Helios Airways Flight 522 - Wikipedia, the free encyclopedia