A good start would be to have Ethiopia conquer the Ifat Sultanate and get into the Red Sea and Indian ocean trade. Conquering the rest of the Highlands and the Somali states should allow for greater domination and a larger presence in the trade, which will allow for a larger presence in the Indian Ocean.
Eventually, Ethiopian sailors discover Australia and found trading posts, which slowly yet surely become colonies.
Worldwide, this really alters the balance of power in East Africa in Ethiopia's favor. Should Portugal turn out like OTL, she will be a big competitor with Ethiopia.