V12 diesel engine; way to go for efficiency. Junkers were using BMW diesels back in the 1930' and I believe a large percentage of German WWII bombers were diesel powered.
The major airframe manufacturers are working towards no windows, just Hi-res LCD screens
8 hrs single pilot, probably with zero pax or freight , otherwise a more mundane 4 to 6 hrs, no problem, common everyday pre flight consideration
Lear Fan proved the concept of a single engine 'pusher' design albeit with two engines and a combining gearbox, the issue will be Paying pax and S/E and IFR. It took 20 years for EASA to recognise C208, PC12 etc as safe for S/E IFR commercial Ops.