Some one makes one that sits on a flat bet truck or trailer (extreme 4x4 on spike urban gorilla trailer build). I have pictures of a late 60's pop up tear down on my build (I'm that guy) and they are about 2 good bumps from falling apart the new ones are about 1 bump away. Look at popupexplorer.com for quality builds those people know the pop up like these people know overlanding. Buy as old as possible pop up for the hardware, lifts, slides and all the bits and pieces then plan on new siding, canvas and every scrap of wood.
You can look at the album in my profile for more pictures of the teardown.