Anfi
Interesting discussion but I will have to leave the math to Shawn!
Curious when you refer to several issues that are not risk related ie payload capacity - yes has an effect on risk in number of trips and exposure but no impact on an individual flight. More of a commercial concern.
Why would a dual engine helicopter have assumed worse auto performance design than a single of the same weight? Because designers are anticipating an engine failure?
For offshore flying floats aren't required for an engine failure, they are required for any event that can put you on the water. And I agree it is far too frequent at this point in time.
But my biggest question would be a definition of a "safe and assured landing area". Sounds simplistic - What is that? What weather do you require to assure that? Day? Night? How big an area? Will losing one engine require an immediate landing? Can you continue to a runway? What about a tail rotor problem? These all can be handled very effectively with an appropriate landing area but it isn't a farmers field for a large helicopter, nor is a farmers field required. A landing at an airport would be more appropriate for all these issues.