Ethnic federalism needs to end, look at how Kenya is thriving without ethnicity based regions. Ethiopia must always be indivisible.
Ethiopia is one nation with one nationality for one people
The only place where ethnic federalism us not working is in Woqoyi galbeed Somalia.
Kenya has counties which resemble ethnic federalism.

I'll ignore your joke about SL
Look in Kenya the NFD became broken down into 3 counties named after cities (Garissa, Wajir, Mandera). Similarly DDS should be divided into 5-7 each named after its most important city.
While the world is neutral on SL becoming a separate country i honestly believe that the West, China and Russia all strongly support a united Ethiopia. TPLF won't support secession because of their Western supporters