The QuinetiQ report is badly flawed and was not subjected to interested party comments and peer review as the JAA and the EASA had no experts or peers to review it.
When reading such a statement it would of course be helpful to get a reaction from QuinetiQ as well. And to see the comment QuinetiQ wrote about your report (which, I assume, is not peer reviewed either?).
Anyway, this is all about statistics and obviously the statistics (accompanied by some lobbying work I suppose) have convinced most/all aviation authorities to allow commercial IFR operations of single engine turboprops. So be it.
However, when it comes to actually flying such a thing at night over hostile and deadly ground (like mountains and icy waters) it is no longer a statistic, but a very individual challenge for the pilot who sits at the controls. Some of us can obviously accept the situation, others can't. I only ever had one sleepless night before a flight. That was when I flew commercially on MEPs (which I still consider safer than SETs) and was facing a particularly difficult flight which was on the very limit of everything (range, payload and weather). After successfully completing that flight I promised myself that I would never again fly commercially on a piston aircraft. I still fly them and instruct on them and enjoy it a lot, but no more under the pressure of flying commercially. And I know that I am not the only one. It is an individual and emotional topic.
We are humans, not Vulcans, and therefore not able to completely suppress our emotions. Those emotions can turn the most beautiful job in the world into sleepless nights even if statistics tell my analytical mind (got myself a ph.d. in aerospace engineering in another life) that everything is going to be all right. And as I really enjoy sleeping well, I insist that my employer honors my one and unique life by putting out enough money to pay for a second engine.