I always had my doubts about the high level of the fridge.
The lowest it can go, the better, for access. There was a thread somewhere, some time about a fridge slide system that not only slides out, but then lowers the fridge by something like 200mm. I liked that one.
After you have sorted out the fridge, the rest is easy.
When i planned mine (which never materialized), I planned it on two slides only.
One for the fridge, one large one for the rest. The large one can have separate compartments for the different items you want to store.
My "expedition vehicle" would have had more than the rear packing system. It would have had a suspended cargo matt, as well as a full length roof console.
I find the small items (camera equipment, jackets, knee blankets, snacks, cell phone chargers, binoculars etc, etc) are as large a problem as the large ones.
As the kids grow up they will need more storage space as well.