@ Lu, really impressive mathematics,
but one of the "fly by light" ship advantages is the reduced total number of control system moving parts (always a sensitive issue on rotorcrafts). And anyone on that kind of business knows that electromechanical parts doesn't have the 10-9 failure rate.
The mechanical emergency controls came to the ship on the last design phase to serve as an "ultima ratio" (last exit) part and should not be used under the normal and experimental modes. The "normal" bypass system for the safety pilot is the "fly by light" system.
If they had ordered a chute for the crewmembers as last chance exit, how would you define the fail safe rate of that old textile? 
Additionally, as Nick explained, fly-by-light offers, at least theoretically, total resistance to electromagnetic control interference. Some losses of fly-by-wire dependent helos in military training and testing exercise have led to concerns over the battlefield robustness of fly-by-wire systems. Practically, incidents of heavy electromagnetic interference encountered around high-tension power transmission lines have resulted in control troubles for some tech-heavy helicopters and fixed-wing aircraft.
Using your Algebra, what's the all around failure rate on the good ol' but most used crafts? And should we are mad to go up and away with the ships?