Yeah this would be a huge cultural issue. Oppression would return once again because the native people who've been there forever wont like this . That's basically the same strategy the boers had or the Americoliberians had which led to a bunch of civil wars in the country they moved to.
I think a more practical strategy would be to divide between all the countries for social harmony. When you consider the 1.3 billion population of sub-Saharan Africa, our 30 million non-immigrant black population is only 2% . You can easily fit this into several countries without destroying the social fabric of these countries by dropping 30 million people into a country with only 3 million people like namibia
It also isn't uncommon for an ethnic group to exist in multiple countries due to how arbitrary the borders in Africa were drawn. For example the hausa are spread between Nigeria, niger, parts of ghana, parts of caneroon, and parts of ivory coast. On the Eastern coast of Africa you have groups like the masai livinig in both tanzania and kenya or various luo subgroups living in keyna, south sudan, uganda, and a few in tanzania. So a distributed ethnic population is not without precedent.
Personally I'm of the opinion that integration within these countries isn't that hard. It's just a matter of picking one of the countries out of dozens that you jive with, and picking one ethnic group to learn the language of , and assimilate by picking up their cultural norms and buying into the local economy. I think the idea of going there and trying to be your own separate entity is a recipe for conflict. The goal would be to try to go native, not to be an autonomous region within a country. This was the critical flaw of Liberia.
