In other words, it is damn if you do damn if you don't. 
Do Oromos need to maintain Ethnic federalism ?
The answer is no. Oromos make up the majority of the country. In a democratic state, majority rules. If Oromos and Amharas join forces, power remains in their territory. What about if undemocratic forces prevail, Oromos are already armed to the teeth. Who really needs Ethnic federalism, you guessed it, It is Tigray. As Ethiopian central government finds it difficult to maintain Ethnic federalism, Tigrayans will pave the way to the impossible. Declare independence. For one thing, Tigray's boundary is not delineated. Tigray lacks legitimacy from the international laws perspective. For Tigray, it will be back to the future. In other words, it is damn if you do damn if you don't.
In other words, it is damn if you do damn if you don't.