On the subject of 4x4 overland vehicles, I gave this a lot of idle thought some time back. I like hardcore offroaders, but the reality is that you just dont need them 99.99% of the time and when you consider the cost, maintenance, fuel economy and upkeep of something like a Unimog, it's a bonkers option. Seriously, how likely is it that you will ever take a camper van rock-crawling? Consider how tall they are too? You'd be taking branches off trees and grinding under bridges all over, with some seriously limited access in towns and the like. That's not a good brief for a camper, even one that needs to be rugged. Also vehicles like Defenders and Land Cruisers, while excellent offroaders and good cars generally, are just way too small to "live in".
There is a solution though, I give you the Mercedes Vario 4x4....
All wheel drive, traction control, ABS, good ground clearance, ladder chassis, live axles etc. There are about 80 model variations to choose from, but this one is the double cab chassis back.
http://media.daimler.com/dcmedia/0-921-656624-1-1385322-1-0-0-0-0-0-11702-656174-0-1-0-0-0-0-0.html
Give it a suspension lift, some mud tyres, a bit of armour and put a custom back on it and I think it'd be perfect. Lot cheaper than a Unimog too.