I think it would be virtually impossible to ride this thing if it didn't have rate gyros and a microprocessor for motor control to stabilize it. My guess is that the weight shifting is just used for changing the attitude to move in the desired direction.
This seems like a common engineering problem. If you distribute the lift between several motors and the failure probability for a single motor is low enough the probability of an accident can be made as low as for any other type of aircraft. One noteworthy point is, that electric motors are able to deliver a peak power 2 to 5 times greater than continuous power. If that is only for a short time it would very likely still be sufficient to ensure a safe emergency landing, since if some motors fail, the others can take over.