There's no denying that most ethnic minorities would opt for federalism.
The problem is how to make all regions independent first before federating.
In your opinion, how should we (supposing Congress does represent us) do it?

we should promote multilingualism.

i doubt it will happen, the people from NCR cant afford to let it happen! or else NCR will collapse,demise of the glory days!

then let's move the capital first to another area first.

There are no ethnic majority in the Philippines. What you have is a plurality of
ethno-linguistic groups: Tagalogs, Ilocanos, Cebuanos, Tsinoys, Tisoys, Igorots,
etc. There is no need to create independent states before federating. For example,
the U.S. was born out of the original thirteen British Colonies. Once they decided
on a union, the colonies then formed their own states. Similarly, when the U.S.
annexed California from Mexico, the Ango-Californians had already declared a
somewhat rudimentary "California Republic" following the Bear Flag Revolt. The
State of California was organized thereafter.

geez, do you really know what is the Philippines?

our country is a good example of diverse country, the Philippines is full of different but related ethnic groups.

and since regionalism is very strong here, it is inevitable that some tensions will grew between the different ethnic groups especially the major groups and it will just cause for the inferior ethnic groups to seek for independence.

meh, a good example of these is the tensions between Tagalogs and Visayans, and Moros are also a good example since they are seeking independence

It's not necessarily ethnic tensions that causes people to seek political independence. In fact, ethnicity has very little to do with the right to self-determination as guaranteed by the UN Charter. In other words, just because you're an ethnic minority does not mean your ethnic group has the right to form your own sovereign and independent State. The moral and legal claims of the Moro peoples to create their own State separate and independent from the Philippine State rest on the historical existence of the Bangsa Moro Nation. Because Filipinos and the Philippines are colonial creations (first by the Spaniards, followed by the Americans and now the Catholic Church), the Moros have never been Filipinos and never became part of the Philippines until the mid-1920s when Christian Filipinos settled in Mindanao in large numbers displacing them from their homeland. From the point of view of the Moros, the Christian Filipinos are "squatters" who should be expelled and driven out by force and violence. That is, their struggle for political independence has nothing to do with the ethnic tensions between the Christian "squatters" and the Moros in Mindanao.

What is the moral and legal basis of the Filipino Nation and the Philippine State to claim jurisdiction and assert sovereignity over the Moros and their homeland Mindanao? Nothing. What you have is a Christian Filipino "colony" founded after the Americans handed control of the Philippine Colonial State to the Filipino "Illustrados" who were nothing more than a criminal caste guilty of high treason by collaborating with the Americans during the Philippine-American "War". Since the 60s, the MNLF and now MILF has challenged by right of arms this illegal occupation and subsequent colonization.

By the way, Macario Sakay did form the short-lived Katagalugan Republic shortly after and the Federal Republic of the Visayas was declared shortly before the Philippine-American "War". Both had nothing to do with ethnic tensions between the Tagalogs and the Visayans. In the case of the former, that was the original goal of the Katipuneros. In the case of the latter, it was a profoundly spontaneous and natural expression of their national identity as distinct from those in Intramuros and Binondo (the two districts) comprising the colonial capital of Manila during the Spanish Colonial Period. For example, Rizal and the "Illustrados" were Hispanized Filipinos who spoke and wrote in Spanish. They sought Spanish Citizenship for Filipinos and wanted the Philippines to become a province of Spain. Even today, Manila is still very "colonial" without its own cultural identity. This is the reason why Visayans have created their own distinct Southeast Asian Islander identity.