Nigel,
Consider the USMC uses Kaman K-Max's to do underslung resupply flights in Afghanistan using pilotless aircraft. I am sure the cost of equipping the aircraft to carry out that tasking is substantial but as you point out, the technology to do it without Pilots exists so why should it not be feasible to do it with pilots monitoring the process.
I guess the big hurtle would be to find a way to keep the Pilot from interfering with the Auto Pilot system.
