Hey @Emanuel,
Apologies for delay, came back from camping to an avalanche of work.
Here are some photos of the platform, I've included photos with everything set up for overlanding, and when mostly empty (for dune bashing), so you can see the platform clearly and in context.
The idea was to use the XJ for dune bashing and overlanding... both have contradictory needs, so I tried to marry them together.
The platform is all-aluminium frame, with plywood platform. I didn't want drawers, because those add weight and minimise flexibility. Instead I can slide in storage boxes, tools, and anything else, where it's needed.
The frame lip at the back of the frame holds the boxes and bags secure, while the lid itself holds everything within the platform storage space. When I lower the lid, it acts as a table I can cook on, work on and eat on, etc.
The fridge was chosen specifically because the lid opens both ways... so I can access from inside or outside the xj. And with it right behind the driver, I can even access it while driving by reaching my hand around. During dune bashing, I replace the heavy fridge with a lightweight cooler.
Clearly I had to remove the rear seats, but there is also space under the frame to the floor of the jeep where I can store even more things.
The platform needed to be set up so I can sleep inside. I also have my spare tire in there for when I'm dune bashing, but I can remove it and install on a rear hitch tire carrier for when overlanding. I needed the tire outside for overlanding, and clearly a rear bumper would have added excessive weight, so this was the best solution, and I just remove the hitch when back to dune bashing. The large storage bin behind the passenger seat can be opened and closed with and without the tire inside (everything was measured accordingly).
The platform is incredibly light, and can be maneuvered in with one person... although two is better to help with the awkwardness. But I still have the rear seats and can return everything to stock very quickly. Only 4 bolts hold the frame to the base of the jeep.
The tall box on the platform holds water jerry on one end on a slide, and on the fridge side I can install a power bank to run the fridge and peripherals. I remove this for dune bashing because it's extra weight I don't want and the extra power is not needed.
Anyways, I hope this can provide some ideas or inspiration. Any questions, ask away!
XJ Platform.pdf