Do you have any? Lol
So, I want to try and shy away from touching Sub-Saharan Africa TOO much before about the same time regular contact with Europe/Asia started IOTL simply due to the fact that African language families generally remain very poorly understood, without very many proto-languages reconstructed that I can work with. Reconstructing the history of African language families is difficult for a few reasons, namely that many parts of Africa are notoriously dangerous and underdeveloped, which means that there isn't much of an interest locally in understanding linguistic history (more immediate things like food, shelter, power, etc. are more important), and it's not always that safe for foreigners from Asia, Europe, and the Americas to go bantering about Africa. However, another factor that makes it very difficult is the lack of written history, which can be problematic depending on how drastically languages have changed over time. For example, the Volta-Niger of Nigeria, Benin, Togo, and Ghana, to my knowledge are largely tonal and isolating. Reconstructing Old Chinese is hard enough using the Oracle Bones, but if it weren't for them and China's extensive literary tradition in Middle Chinese, then it's entirely possible that we never would have been able to sort out HOW exactly Sinitic languages relate to Tibeto-Burman languages, if we would have been able to at all. That kind of material isn't there for Africa obviously, so... yeah. That's to say nothing of the various "Nilo-Saharan" languages. Who even knows what's going on there...
Now, in terms of South Africa, as in modern South Africa and possibly Zimbabwe and Mozambique, I was interested in colonizing them prior to the Bantu Expansion into the region, potentially from an Indo-European Persian Gulf, from India (with whoever eventually inherits it), or maybe a more maritime Egypt. I don't know...
I'm fairly positive that the Yayoi are never going to Japan ITTL, at least not as the Yayoi, because their cultural development will have been butterflied away at that point. I was thinking that the movement of Para-Turkic-speaking peoples into Manchuria as spurred by the Indo-Europeanization of the Altai Mountains could push Koreanic peoples up into Siberia so that Japonic peoples can inherit Korea, at least for awhile, before it is Para-Turkified. What to do with Japan, though. I know that I'm pretty interested in keeping China balkanized, so maybe one of the kingdoms begins settling Japan some time in the 1st millennium BC? Just an idea. It would be fun if we could get Austronesians up there, but all the literature on Formosan languages and their reconstruction is in Chinese. What would be even more fun, if I could really pull a rabbit out of my ass, is to get Eskimo-Aleut speakers down to Japan, but I'm not sure how I could do that and also have them not end up marginalized like the Ainu.