The CircleTrip Explorer (fare basis *ONEWC4 and see the rules ex HKG on christep's site) would do the first part of your trip i.e. everything except South America. But you would have to do Oz before Asia in order to get back to Europe for the long break. I.e. Africa/SWP/Asia/Europe/Africa.

If you do it in A the price ex MRU is a steal. In J there's not much in it compared to South Africa, unless you particularly want to visit MRU. And it obviates problems caused by the paucity of flights from MRU to JNB.