Back in the day (over a dozen years ago), BA actually had more than one franchise partner in Africa.

In addition to Comair, there was "Regional Air" based in Nairobi, with service to/from quite some other places, including a daily JNB-NBO rotation, which allowed construction of quite some routings wholly within Africa. If I recall correctly, network included such places as Asmara, Djibouti, Lilongwe, Mombasa, and certainly some others I can'r remember.

Doesn't excuse the poor network today - but at least shows it hasn't always been so isolated on the OneWorld routemap...