I'd like to address the elephant in the room, if I may.
All of these fine examples are pointing to the fact that they aren't meant to Overland in the fashion that we are used to in this country. Myriad of factors such as low clearance, slow top hwy speeds, small tire sizes, etc are pointing to that sad statement. Rather than modifying the platform to suit the application, which usually translates to mucho $$$$ and time, why not look at more appropriate van platforms that CAN do the task on hand? In my travels, I've seen VW Synchros 4x4 as well as Mitsubishi D...... (can't recall the model now) vans going off the beaten path but they too probably have similar limitations.
Overlanding does require, on occasion, to traverse harsh territories/obstacles where all kinds of four wheeling, rock crawling, and recovery work are needed. So this means that your sliders, bumpers, winches and belly pans are going to be used. This is the harsh reality of what we do and for some of us, we call this fun

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While a Sprinter 4x4 van is too large, per Stephen, is there a smaller size van that can do the job? I know that the Chevy Astro vans are using Chevy S10 Transfer cases to switch the van from an AWD to a true 4WD van that is quite popular on expo portal. Conversions like Quiegly and Sportsmobile seem to be popular as well.
Some more info on vanlife on Expo
4wd (and 2WD) Camper Vans (a.k.a. #vanlife)
just playing devil's advocate here.