I had the same problem with my old Class A,not enough storage for the same things you want to take along.
I thought about a rack on the rear, as you did, but that old P30 Chassis with the short wheel base and long overhang with the fuel tank in the rear, made it overweight when fully loaded. I had no extra to play with. The front axle was way under from its Max capacity,so I needed a way to transfer the weight up front.
My solution was to mount a
Cargo box on the roof as far forward as I could. I mounted it cross ways with the hinges facing forward. It was large enough to put my EZ UP in plus a few bundles of wood. I also used it for other heavy things like cases of drinks.
I have seen others that had fabricated a box on the roof to do the same thing.
This did transfer weight to the front axle,and gave me more storage space. I also used
one of these that I modified a bit to haul my wash tub fire pit on the rear ladder.