Re: AwesoMe one here!
I think those black lines are rubber bumpers, so I would agree with Gnarvan that it was used as a work platform. Notice that the front of the roof extends beyond the front bumper. Must be a ladder on the back (but there's no rear view shown). The front of that roof appears to be sealed off from the inside starting from where it slopes up, so it doesn't appear to be for internal storage, either.
2008 E350 EB, V10, GTRV Conversion