I like the idea of minifactions, if only to act as wildcards in scenarios and campaigns and such. If someone wanted a challenge they could even be playable. Though I don't think we'd make any effort to include them until at least after the Seleucids are done, I'd see no harm in actually creating and researching their civ profiles. For a particular "African" minifaction like the Bantus, like you said, we could probably only be 20% accurate with the references and resources we have available, so I think it's okay to incorporate texture ideas (like for shields and such) from other nearby peoples.