Here's another one with a RTT. I think the setup is too slow for overnighting. It might be fine if you camp in the same place for several days.
Also, I see a lot of drawer systems on "overlanders." The drawers are convenient but don't seem space efficient. A shelf (or the top above the drawers) allows you to stack things in the cargo space while being able to pull things from the bottom of the stack without having to unload the things on top. Adding slides takes up more space though, and rectangular drawers leave unused space around the wheel wells, and in the wedge behind the seat back (if you're using the rear seats). Soft bags pack more space efficiently, and they're better at preventing items rattling in the empty space of a box or drawer.
I don't use a shelf in my Rover because I use the cargo space for a large dog - too large to lift him off the floor significantly.
I did just add a Pelican case to store all my hard items (bottle jack, socket set, wrench roll, hi-lift, hammer, shackles, ****** block, etc.). Before I had some of them in a tool bag, and others in various cases. It's important to stow this kind of stuff so that it won't go flying in a sudden stop or minor collision. The hard case is more secure than a bag for those very heavy items, and I have strapped it securely in the cargo space.
The Discovery has been criticized for being very inefficient and lacking in cargo space (compared to a Defender or 70 series Land Cruiser). I do find it lacking space when I have it loaded with four people and a large dog, but I make it work. Obviously light and bulky items like sleeping bags, pads, pillows and so on have to go on the roof rack. But when you have all the space for one person and their gear, there's a lot of flexibility to make things convenient. But it takes plenty of experience to know whether you want sleeping space, a refrigerator, a sink, seats, radio gear, tools, or what. Right now, I like having seats. I've seated seven people and a big dog in my D1 on several occasions. It's not ideal, but better than someone missing the trip. I do not want a sink. I have no use for that at all.