Do you know how many ethnic rebellions and separatists Ethiopia has had to forcefully suppress? What are you even talking about?Anyway, if Ethiopia can create an ethnic federation (even if, for the moment, it isn't much of a federation in practice), why exactly can't other African countries do the same thing?
If you are talking about creating states within the country that correspond to ethnic divisions or cultural divisions, that has already happened in many African countries. For example Nigeria is already divided into 36 federal states, which largely conform to linguistic/cultural lines (with a few notable exceptions) and it did that decades ago, so if that is the sort of thing you are talking about that has already been done. If you are talking about actual full autonomy within a country for specific states or regions, that does not exist in Ethiopia, and if such a thing were implemented in a country with unequal distribution of resources (and access to the sea), it would likely result in the eventual breakup of that country (unless some sort of elaborate resource sharing agreement was worked out).