I found, much to my surprise, Ethiopian nations (Axum and Abyssinia) are in fact playable, (due to their religion being an Orthodox heresy) so I decided to try out one. Playing as the King of Abyssinia (the southern one)
Doing fairly well, actually. I conquered the Muslim nation to my east (Harer something or another) so I now control the Horn of Africa. The Shia Caliphate (which is crying aloud for a nerfing in the next patch; it controls everything up to my borders, and up to Sanaa, and up to Antioch, and it did this and more in my Galicia game as well) ate up Axum before I could get there, and I have had to reload twice due to them DOWing me when I have no possible mercenaries and they can field an army 5x my size. Other than that, my country is financially prosprous, administratively very stable, and militarily as much of a power as I can possibly be, sitting in the southeast corner of the map.
I have my sights set on Sanaa (I have not checked if there is a strait from Africa to Aden, it would not make a huge difference either way)
If you are looking for a unique game (Ethiopians use the Muslim char models, but are Monophysite) I recommend Abyssinia.