The Kiravan is a bit of overkill. I would agree that anything with a mechanical primary system - ie older mechanical engines etc, would be more robust, and I have kept that in my Unimog despite seriously thinking about an engine transplant with a more modern, fuel efficient and quieter motor. I have a lot of electronic systems on board mine, granted not as much as Kiravan but not that for off it. None of the extras are essential for keeping things mobile. Being able to use older high sulphur diesel, bio diesel, canola oil and more or less anything that pours was a big consideration as we plan on traveling around the world, preferable off the beaten track as much as possible including Africa and South America. In saying that, I've seen people with newer Land Rover going through some pretty remote places with modern common rail engines with only the occasional failure, mainly due to dirty fuel.
If I was just traveling around Australia, then I would have a modern Cummins B6.7 in there now as fuel over here is pretty good and I've had no problems with my Land Rover Defender Tdci over 120,000km with half of it off-road/remote area. Good fuel filtration is all you need to keep things health, and even an older diesel will stop if the injectors are plugged with dirt, just takes more of it.
The trailer will make thing difficult, and you won't get permits to travel with it on a lot of the remote tracks, but if it can be unhitched and you can travel comfortably without it, then it would be great. Hook back up with the trailer when you planned on camping up somewhere for a week or month. It would be a bit of drag pulling across the 1000 sand dunes in the Simpson desert or the Canning Stock Route, but could be transported around to meet up with you at the next big town.
Anything from Mercedes and ex-Military would be serviceable almost anywhere in the world, and they have a great dealer and independent parts supply chain. I can still get new parts from my 1984 Unimog because it is basically the same truck in production and used by a lot of countries around the world. That's the main reason we went with Mercedes.