>>2314574 from what I learned using my wagon with no permanent fixtures I would suggest a setup like this. if its rainy or windy it will put out your cooker you want to be able to cook inside. you see setups with the kitchen at the rear door but you have to stand outside for that.
have a portable toilet under there bed because if you are in town you cant use the bushes.
have the bed at a height just tall enough to sit up so you have the most storage underneath. have water storage and an empty water storage the same size for waste water under the sink