The problem with african units arrises not in early or late units, its the Mounted Units. Other than Zebra Rider and Zulu Cavalry, its pretty slim pickins. I understand that there were no real African Knights or Cavalry...but thats never stoped us before!
Middle Eastern Musketmen, Riflemen and Infantry are also rare. There seems to be more for Meso-America than African and Middle Eastern for these units.
Thats not to say there is nothing out there, but come on, do we really need another European Dragoon? And I am pretty sure we have every airplane ever built in every color combo imaginable