Your best bet would rerouting the Bantu migrations north via the Great Lakes into the White Nile. The best candidate for this would be the Urewe Culture (Proto-Eastern Bantu). As they migrate, they pressure the native Nilotic peoples north into Meroe. A historical parallel to this is the fall of Rome, with the Huns pressuring the Germanic tribes south into Rome, leading to its collapse (I'm oversimplifying, but you get my point). For the sake of the scenario, a similar thing happens with Meroe, but on a smaller scale, so that by the time the Bantu arrive (assuming the migration north starts by 500BC, let's say it reaches Meroe by 200BC), they find the kingdom a shadow of its former self, with several rival successor states of mixed Kushitic and Nilotic descent. They are able to assimilate the Nilo-Kushitic peoples, and they adopt the Bantu language and culture.
If the migration keeps going, they can either continue into the Nile proper and reach Egypt or follow the Blue Nile into the heart of Ethiopia. If they continue into Egypt, (my estimate is that they reach Upper Egypt by 1AD), they can serve a role similar to the Blemmyae, a buffer tribe for Rome protecting the southern border from invaders. Assuming minimal butterflies, they could carve out Egypt from the Romans during the Migration Period. From there, they can expand further into the Levant.
If they go into the Blue Nile, they can assimilate the Axumites into the Bantu culture. From there they can migrate into East Africa, and like @EparkusTonTrapezous suggested, cross the Straits of Mandeb into the Arabian Peninsula. An interesting possibility is a Bantu *Islam emerging from the Arabian Peninsula and spreading Bantu language and culture the Middle East, North Africa, and Europe. However, this might be too much of a Bantu wank.