Hi Paul, it sounds like you are very open to adventure and getting off the beaten path. Depending on your budget, and to maximize your time, what I would suggest is something like this:
• Join an overland for a Victoria Falls to Cape Town trip (approx 3 weeks). This will get you to the Falls, the bush in Botswana, both Chobe River and the Okavango Delta (unparalleled game viewing), through all of Namibia (Etosha, Swakop, Fish River, Soussosvlei) and then down the western coast of ZA.
• From there, I'd hang in Cape Town for a couple of days, and then work my way down the Garden route, hitting up a couple of beach towns and smaller reserves along the way (Tsitsikamma National Park, Addo Elephant Park).
• Then I'd do a section of the 280 km Wild Coast Hiking Trail in the Transkei. You can backpack/hike along a network of trails, either camping or staying in traditional Xhosa huts.
• From there you could consider chilling out at Bulungula, a Fair Trade Lodge run between the entrepreneur and the community.
• After this you head up to Durban for those beaches in Kwazulu-Natal. The further north you go of Durban, the less crowded the beaches. And again, once you hit the wild coast, south of Durban, its very secluded.
• From here you could head up to the Drakensburg and hike in Royal Natal and Golden Gate.
• Then back to Joburg to pick up a car and head for the Kruger, or you could organize a couple of day safari through one of the multitude of tour operators.
• Then off back to the tail end of wine fests in Germany!
My favorite places? I love Zululand, Hluluwe-Imfolozi, Mkuzi, and Itala are some of my favorite reserves. I love the Kruger. There is something new there every time I go. The northern region of the Kruger is something very different, however not widely visited. I spend a lot of time in Joburg visiting friends & family. Just did a safari in the Kalahari, this time in our own 4x4, and it was an incredible experience. That is something you could consider, since you love the desert. It's a very subtle experience. Not big on game, but big on spaces and little things (bugs, scorpians, etc). I loved Mozambique and would love to go back and explore it more slowly. Botswana is unprecedented for unique game experiences. One of my fondest memories is that Chobe River Cruise, beer, binocs and animals. What could be better! I think the best part of all of these places is the diversity of cultures and peopoles. You will hear a different language at every turn. People will always wave back to you. There will be bigger smiles than you have ever seen! The South Africans are truly a warm and friendly culture, from the Zulus to the Afrikaaner. And the food is divine!
If you would like more personal recommendations (ie. rental car agencies, overland operators, places to stay) send me a pm and i'd be happy to pass them on! You will find several threads here on tp about overland companies. Good luck with the rest of winter, and small world, Paul from Munich, My sister lives in Esslingen.