Good one Jeff! "a single Kelly controller...." :-)
Yes.. 3D travel does kinda beg for "redundancy" in system design. But even having two controllers could still result in failure when some other "single" part fails. This is a fascinating topic... many moons ago, i did my master thesis on 'fault-tolerant distributed operating systems'.
One good thing about an ultralight i think is that the aircraft itself is designed to fly (glide) down in case of some issue.
Yes... it will be a while before we see the sky filled with people commuting to work using electric ultralights... we need to first agree on drone (quadcopter) regulations... :-)