South Africa only belatedly announced their initial entry requirements yesterday ( to come into effect from today ) - from what I've read it's all a bit vague so doubt your question about same day transit would be answered for example .. I would predict they'll change a lot before Christmas ( stuff like allowing Brazil and India but banning most of their largest European inbound tourism markets where the situation is better makes very little sense for example and would be surprised if it lasted - though what way it may change ! ) ... I'd say making complicated contingency plans like this so far in advance probably pointless, if I were you I'd sit tight and start worrying about it in 6 weeks time maybe when lots of things may have changed and SA requirements may be a bit more 'concrete' ... I'd like to get to SA around Xmas too, but for now I'm not doing anything about it as it would seem pointless trying to second guess regulations in the medium term.