I just re-readthe thread, and Steve76 says it all.
What we want is improved safety, not necessarily redundant engines. Let's all try to remember that safety does not come from mere redundancy.
I would wage that were it possible to magically make all helicopters full Cat A twins, the accident rates would rise, since most accidents have nothing to do with engines quitting on their own, accidents usually depend on pilots running out of fuel, or into the ground, or some such thing. If we improve the Cat A performance, we make the helo have less range, and you will probably increase the acident rate, when the aircraft hits the ground/wire/trees with two big engines.
I advocate no hard rule on improving aircraft, except to work constantly to fix what goes wrong with the whole system, of which the airframe is actually a small part. Examples:
Fix the airway infrastructure and operating rules, so we have good helo IFR procedures and routes (No more CFIT). Fix the helo flying so we can control the thing at night and in cloud (No more brownout or mis-orientation accidents).
Can we think of other things to fix so that we actually raise safety?