I've been driving Toyota trucks with rotary Denso injector pumps continuously since 1993, first the 3L engine in a Hilux, then the 1HZ in my 80. Those pumps are tougher than you think. I had the pump rebuilt on the Hilux at 500,000km. Not because there was anything wrong, just because I thought it was time. Cost me $1200AUD, plus $300 for the injectors. I had the injector pump done on the 80 last year, first time it's ever been serviced in 25 years of operation. They ended up replacing virtually every part, including the housing, due to general wear. It was still working fine I'll note, just a slight diesel leak from the low sulfur diesel change they did in AU a decade back that shrunk the old seals of pumps, which the new seals fix. Total cost? $2000AUD, plus $500 to service the injectors. Don't look at the Toyota prices, this is a Denso pump, and the parts prices are much, much cheaper through them. All your diesel service places will be buying direct from Denso. That $2000AUD price was basically a new pump assembled from parts. It's now ready to go for another 25 years. These things aren't fragile. You talk about bad fuel and water contamination. The fuel filter has a water sensor on the 80, connected to a dash light and buzzer. You'll know about water long before it reaches the pump. As for contaminated fuel, you can run these engines on used cooking oil. They're not delicate.Well, the diesel engines can go bad easily in my opinion. The rotary bosch style injection pump if getting bad fuel or water contamination goes bad quickly and for example, the injection pump for the 1hd-fte costs 6500 US dollars in the Toyota dealership in my town. The set of injectors are around 3000 dollars. If I take the 1FZ engine for example I can't think of any component in the engine which would be similarly expensive as for the 1hd-fte.
And now consider what the diesel models don't have to worry about. I have no ECU. No fuel pump. No carby. No O2 sensors. No cats. No vacuum lines for the engine itself (on the 1HZ at least. No PHH! The pump is sucking diesel directly from the tank itself, and squirting it straight into the head. You need fuel and air. You don't need spark. You don't need electricity at all. The engine has no weak points. No minor thing I can think of that takes you out of action. There's a reason they're popular in places like Aus and Africa, when being stuck somewhere can actually be deadly.