I can't think of a better way of doing it, at that scale, than Mithadan's, to be honest. I think that if you want to split up your "African" civ then the main divisions will be east, west, and southern Africa, so if you can only turn it into two rather than three, you'll have to choose. Personally, if I had to choose just two, I would probably have one for West Africa and one for East Africa and leave the southerners out, but that's just because I know less about the southern civs. Also, I think there are fewer units suitable for southern Africa than for the others now. Even so, lumping all the eastern ones together is not ideal. I might replace East Africa with just Ethiopia, since that's a more major and interesting civ than most of the others around there (controversy!). I think the west African civs are a bit more similar to each other than the eastern ones are to each other so it's probably not so bad to lump them all together. You could use some of the more primitive-looking African units I've done before (the generic "African Archer" and so on) for the earlier units, and then use these Benin ones for later units, perhaps; and then you could use the Ethiopian ones for east Africa, or Ethiopia, or whatever.