You are most likely looking at heavier duty Class 7 or 8 toterhomes with garages on 22.5" wheels to get the capacity and longevity you want. When I was looking to replace my toy hauler with a motorhome pulling a 10k lb enclosed trailer, I only found the largest Super C and Class A pushers with sufficient payload and receiver capacity and they were too big for the areas we visit once you add the trailer to the length - This was not even the type that had a garage with any appreciable payload.
Towing capacity was one of the reasons I went to truck campers - I have upgraded to bigger trucks and campers since I started, but still find that the best combination for me. I have a 20' enclosed trailer that carries my toys or a Chevy Sonic behind my 11.5' triple slide. The 6000 lb camper along with the tongue weight of a trailer typically loaded 6000-8000 lbs required my Class 5 truck. With my current setup I am under 55' overall length and can tow up 12,000 lbs. I have also looked at other options that would allow me more tow capacity while still keeping the same truck and camper.
It sounds like you want to avoid towing something - If that is the case, you really need to look into the toters...
