Autofeather, etc.
Autofeather a la DHC-6 works by comparing the torque on two engines, doesn't it? So there's no way you could fit that to a single. There must be a specific drill for engine failure on a C-208 that has one feathering the prop after an engine failure. The risk associated with autofeather is that it might throw a wobbly and feather a perfectly good engine. That's why we only use it for takeoff. It's not a magic pill.
I try to always have my glide speed or Vx in mind, so that when that evil swine at the back of the sim slips in a total loss of power I have a snappy come-back while I figure out what to do next. But in real life there are places you could do everything right and still end up dead, either from the crash impact or else from exposure. There I just wouldn't want to be in a single if I had the choice of a twin.
There was a crash of a Piper Tomahawk down in the Carolinas a long time ago now, when they lost their magnetos at night over the piney woods. The pilot, an instructor, did everything right within the limited options available but both occupants died when they hit the trees.
Under normal conditions in much of the world if you end up in the water without a survival suit all that a life jacket will do is assist in the recovery of your corpse, unless you are extremely lucky. Check out what happened after the Air Florida crash, right in the middle of a major American city, when people ended up in the Potomac River. In winter you have a couple of minutes, max, before your body stops obeying your commands, not much time at all.
I had a job once flying what one could fairly call junk airplanes. Sad old Travel Airs (160 h.p. per engine) loaded up with four big, fat Bahamian market ladies going out of Miami on a hot afternoon with all their shopping back to Freeport. The rate of climb on two engines could have been measured with a calendar, so that if I had lost one I wouldn't have had many options. There I would have been just ever so happy to have been given a C-208 instead, I suppose. They hadn't been invented yet, plus they cost serious money relative to a clapped out Travel Air.
But then I would get these runs at night from Great Inagua back to Miami over about 400 miles of water, mostly. The so-called Bermuda Triangle, where it's quite easy to vanish without a trace. No little green men, just lots and lots of water and very few bits of dry land. Then I wanted two engines, minimum.
The thing about the Navajo is that it's often a rather tired, not all that easy-to-fly airplane flown by a low-time crew. A recipe for accidents, yes? I remember a typical accident, where the pilot lost one engine early in the takeoff roll and continued down a long runway until he lost control due to Vmc, trying to make it fly on one engine. Doh! (That was when the FAA changed the rules to require ATP licenses for air taxi pilots. After that we started having a much better class of accident, I guess.)
I guess the thing is, as a pilot, you have to take the risks as part of the cost of joining the club. The real problem is that the passengers often naively expect that boarding some little bug smasher piloted by a pimply kid on a day that the birds are all walking is just as safe as flying with a major airline. Well, thanks to the magic of 'code-sharing' sometimes they expect the major airline and get the bug smasher! Then, when the inevitable happens, flocks of lawyers descend to profess themselves shocked, just shocked by what they find about the risks their innocent clients were exposed to.