The one vice more engine debate re IFR/IMC does get confusing. Is it the redundancy the second engine (or more) brings by having a second generator or the ability to continue flight following a single engine failure which by definition single engine aircraft cannot do?
I am of the mindset the twin engine, fully IFR kitted aircraft, combined with training and experience both accumulated and recent to effectively continue flight in IMC conditions (whether intentional or inadvertent) is the answer.
Without the training and experience all of the fancy gadgets in the world will not prevent bad things from happening. The flip side of that coin is without sufficient equipment on the aircraft....no amount of experience and training will overcome that and then too bad things happen.
Add in the collateral issues of weather reporting, landing aids, communications, operation safety culture and all the rest have to be in place as well.
Therein lies the challenge to the HEMS industry....how to accomplish all that and do so in such a fashion as to remain economically viable.
Perhaps there is a compromise between the UK/EU models and the US models that ought to be considered. The US view of providing 24/7 service of equal capability might need modifying.
At least under the US FAA system there is the flexibility to be able to accomplish that as compared to the very highly restrictive UK/EU/JAR/EASA system.
I for one would much rather be in the USA when I have my life threatening experience and need emergency transport to a Trauma Center. If that need is at night......there is no comparison between the US system and the UK system that gives one comfort about the availibility of HEMS service at night if you are not in the USA.