The Southern African Development Community looks like the perfect root for an African superstate.
Linguistically, the states of SADC (and most of the states of Central Africa and the Great Lakes region) are largely populated by speakers of Bantu languages, including KiSwahili, isiZulu, chiShona and kiKongo. This common linguistic heritage, spread out over such a vast geography and its natural resources, could reasonably lend itself to a state which governs over a third of the continent.
Politically, a Bantu superstate would be the most visible representative of the African continent to the international community. It would also reduce the visibility of internal ethnic rivalries and any specific exploitable natural resource (such as oil, minerals, etc.).
Finally, it would be the best way for an African state to ably exit all of the many post-colonial federations such as the Commonwealth and La Francophonie, while using the government and diplomatic apparatus to highlight and export a more uniform amalgam of Bantu culture and language to the world, especially to the African diaspora in the Americas.
Let’s call it the Bantu Republic, or Azania.