I'd probably go with a roof mounted unit, or two, with a breaker box to handle that... And... Have you considered doing buggies like that for folks who are into "I need my workshop along" stuff like Benchrest target shooting? Because, damn, if I hadn't fallen in love, and ended up living in my van down by the lake for a couple of years, and then clawing back, I'd be all over that.
We had a LOT of guys who would set up the enclosed cargo trailers, because they had the weight capacity...