I think Ethiopia is the best choice.
First, the problem is to be protected from Europeans. Japan was even before Meiji too powerful and too far away to attract European conquerors. Ethiopia would at least be too far away before the Suez channel was built.
Nevertheless, you'd probably still have to predate the Meiji some years - or at least take a prior POD which lets Ethiopia become stronger before Meiji takes place.
Preferring British advisors and providing trade opportunities for Britain might help as well. In a sense, Ethiopia could behave like a de-factor British protectorate until it is strong enough to become an official ally, just like Japan.
Another problem will be that Meiji in any African state should be slower than in Japan due to the lack of educated people.
Well, first of all you need to get rid of the era of Princes, when Ethiopia was split in several Amharic and Oromo kingdoms, and only reunited in 1855. Also, Ethiopia was an expanding empire during the 1800s. Since the reunification under Tewodoros, Ethiopia expanded to the lowlands, subjugating several peoples.
Ethiopia's problems are several though:
1. Ethnic diversity, rivalries between Amharas, Tigray and Oromos, between Christianity and Islam. The Oromos seldom felt loyalty to the Imperial Crown, and for example betrayed Ethiopia during the Italian invasion 1935-36.
2. Feudal Society: the emperors were weak, the provincial governors acted as kings in their provinces. Also several plots and uprisings by dissatisfied nobles. Some emperors were deposed etc.
3. Serfdom and slavery: The peoples of the Lowlands usually became serfs under Amharic soldiers and officials. Slave raids were carried out against peoples both inside of Ethiopia, and outside, which pissed of the colonial powers (several raids in British, French and Italian territories)
4. No access to the sea, an early POD could of course change that.