i did read that some ferries allow you to stay in the camper on some s africa to s america routes. others may too if you wanna go by slowboat too.
also if just left on the open type pallet, that you have to expect it broken into, what else will the crew do during the trip!?!
some have fitted small metal wheels, just to get a mog into an enclosed container. portal axles may help with minimising their diameter? do the standard wheels with no tyres give clearance? will that damage them???
or had 3 secure boxes made with proper locks, that seperately fit thru the door, but once inside, you bolt them end to end to each other and to the floor, dimensioned to be a snug fit making it much harder for them to pilfer. but lights, mirrors etc..... fair game!!
we are currently mid purchase of a mog camper thats spent the last 5 years touring, has been to panama etc, and is a little taller than what i would have built myself probably totally ruling out the smaller wheel approach, so ive been scratching my head for solutions too. good luck!