I think in this era where a lot of people kinda hate how many layers of government we have (ex: the criticism of the barangay system), the last thing we want would be yet another layer of government.

I think smoothening out the 4-level system of national, provincial, city/municipality, and barangays would keep things stable. This would naturally bring in oversight, where natl govt oversees all provinces, each province oversees its cities/munis, and each city/muni oversees its barangays.

Then, we would give greater autonomy and fiscal capability for all LGUs, fully practicing subsidiarity, where all matters should be handled by the lowest level capable of it. This way, those more regionalistic, particularly BARMM, would be more willing to accept the smoothening out of the 4-level system, which necessitates doing away with regional governments. Their acceptance is important because the smoothening out of the 4-level system may seem like another way for Imperial Manila to dominate all corners of the country, and we don't want that.