Some comments on the excellent responses above:
I have copied all the comments and will compare tham, cross plot them and generally bend and twist them until they prove what I want .
Seriously, I will use these answers as fodder, should I ever get a chance to again help develop a helicopter at Sikorsky (three so far has been a gift, could I wish for one more?)
I note lots of support for automatic parachutes to land safely if the rotor fails. There is an old joke about this from Boy Scout Days - the scoutmaster asked the young scout why he packed the eggs at the bottom of his pack, where they were likely to be crushed. The kid responded, "that way, when they break, they don't run all over everything!"
I would rather ask for a rotor design that was redundant enough so that even with failures, it wouldn't fail to do its job. That is my "parachute".
Regarding changes, costs and tradeoffs, I find that today's system in both Military and Civil development makes costs so high that we end up with too little innovation, and too much of samo-samo design. I wish it were less costly to develop and approve things, so that we could change them quickly and cheaply, and give you what you want.
Regarding safety, I wish we all would look at what actually brings us down, and not what could fail, and fix those problems. One poster above had the key when he asked for one big efficient engine that never failed, rather than two. We should try to specify the root cause of the problem or the worry, and not dictate a design.
Anyway, please keep this going, this is golden!!