I have had some thoughts about this. 8 foot inside height cargo trailer will be less than 10 ft outside. IMHO, not much of a issue. OTOH, a cargo trailer does not have ground clearance for tanks under floor. But mount tanks on top of factory floor, put a floor above them. Forethought on location off tanks, pull-outs at doorways, and you have storage in a location great for hauling heavy things. And removeable floor sections would be great to access thing that you only need to see rarely, like batteries.
If you have a water heater, I don't think a hand or foot pump would work.
Swing rear doors, rear kitchen. Mount stove, sink and or counter to door with some way to slide up/down. Up, use inside. Nice weather, open door slide down, stand on ground.
Dump waste water on the ground? Really? Give approval to that on RV site? Really? What is a better way to reduce the number of places to spend a night.