I would also look at a CX J or F award to JNB via HKG, then pay for the Comair or SA connection to WDH. Note that CX doesn't offer F on HKG-JNB during the northern summer, so it'd be a judgment call to book into J or F. However since the F award is only 20K miles more than J, I'd definitely go for F for the transpac portion at least. CX is increasing their frequency to N. America significantly next year, so getting award seats might be slightly easier.

On the other hand, getting BA award seats to South Africa is like pulling hens' teeth.