The camper might need an extra brake yeah. But you can only have 250w motor here. I was thinking really lightweight XPS with carbon. But the stuff you put in is probably going to be 200kg at least if you want to "live" in it like with vanlife.
There is this "lightship RV" trailer (video) for electric cars that uses this concept of a somewhat round / elliptical shape and lowering top half. But it would need to be lighter and thinner.