My bike stays up while moving forward even if I'm not pedaling. Forward momentum works wonders. Once it's slow enough to fall over, it's too slow to kill or even really injure you. I know you're arguing against the "losing power would kill you", but I would go farther and say that "it very well might" is only really applicable if you stall in the middle of a highway and get hit by another car, in which case even a Volvo would struggle to keep you safe.
Well, my main doubt is in your ability to effectively control the vehicle unpowered. This could be dangerous in many instances: on bridges/overpasses, steep roads, roads with steep drop-offs near the shoulder, etc. Stalling at highway speeds with other vehicles would not be good, but you may be able to manage it.
