In my mom and dad's camper when I was a kid, the overhang (bed) had a ladder. The ladder had two pegs on the side about 3-4 inches long. The pegs on the ladder fit into 2 holes drilled on the edge of the over hang bed, and when turned sideways, in place in the overhang looked like bars on a baby crib (only much wider). It worked very well, the wooden ladder was light enough, that even at 8 years old I could lift it out of the holes, set it on the side of the bed and use the ladder without help. My sisters slept on the bench-table-bed under the front window, and (as tempting as it was), I never clobbered them in the head setting the ladder in place when I slept up there. Maybe you could make something like that. (See my profile -link on the left- for a photo of that camper).