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I totally get you on the challenge of squaring the original plans for the purchase with whatever turns out to be the best fit in the actual circumstances. Having a personal escape may be something you don't fully appreciate the need for until you have the ways and means for it. I find that time on the water can be wonderfully restorative, and I definitely need my regular fix. However, I don't have to be by myself; I love sharing this with others. Family members don't always share that motivation, but sometimes it's a matter of presenting the right incentive. Which can be as simple as an ice cream at the destination, or going out to dinner at a "special" place after an evening sail.
My general advice when it comes to modifications, whether for rigging or anything else, is to try out various things, if possible, without permanent modifications and just gain a bit of experience with what works and what doesn't. I'm excepting a bit the standard improvements for CB control, because you can get very good descriptions here and the need for them does no depend on how you want to use your boat.
The only expedition style sailing I have done on a DS (not mine) involved packing gear, food and a full supply of water for 6 days with reserve and spare parts. After that the cuddy was full. We camped on the beach instead of trying to stay on the boat. Looks like I'm a bit taller than you, and the only time (other than for repairs) that I've gone into the cuddy was to get out of the rain. If I ever felt like setting her up for sleeping at anchor, I would probably rig a small shelf that would turn one of the benches into a sleeping platform. And maybe another, smaller one, to create a "galley" space or table.
For the sleeping platform, essentially, one would fill in the space between bench and center board trunk to the same level as the seat. And make the parts of it so they collapse small enough to be kept in the back of the cockpit. For cover, I would look for adapting something like a small tent, rather than trying to work with using a tarp as a boom tent. I've read a number of descriptions here and depending on what you can get your hands on, there's ample latitude for very creative solutions.
My suggestion: keep the discussion here focused so it (roughly) matches its title, and if you want to discuss specific other mods, just start a new one. That makes it easier for other people to find information that they are looking for.