This may be old news but have you seen the Rugged Mountain Custom RV Denali https://www.youtube.com/watch?v=CsEi_npWrcw As a recent convert to a flatbed hauler, I see this or others as a futur...
Its not heavy for a F550 or 5500. Even with a steel bed you probably have close to 9k of available payload. So figure the camper with full water and propane might weigh 7500 I see plenty of room for solar, batteries and a nice rock collection.