You’re about 50 years too late.
Even arguing that culturally it would be a Good Thing[tm], you still need to show that reverting to some “quaint” cultural identity will actually lead to a greater good for Taiwan. Saying that Taiwan’s national language, ethnicity, practice should now be Minnanese instead of Mandarin is academic. No one has been able to show or argue persuasively that all of Taiwan would be better off in such a state.
In fact, it would be easily shown how bad Taiwan would be if it accomplished such a thing. If you need any such proof, look to Malaysia around 1980s-1990s where they did just that with Bahasa Malaysia language and ethnic identity throughout its school systems. The result was that many Malaysians could no longer survive in an international world. They couldn’t speak the language of business, English (despite the fact that English is one of their national languages). International businesses, looking to Malaysian human resources for their operations found it very lacking. Malaysia could not sell itself despite obvious advantages, all because some people thought it would be great to blow Malaysia’s horn in the world and show how they’ve arrived. Everyone needs to take notice of Malaysia, because Malaysia is great! Well, they’ve reversed themselves and no one is trumpeting such practices. The new PM is advocating and promoting anti-corruption measures, practicing inclusive, not exclusive, politics, and opening itself up to foreign investment and education greater than ever. He knows the world competition is tough and Malaysia needs to carve out its own niche in a brave new world where China will be the Economic Emperor in this region.
All these things is what Taiwan should be doing but is not doing. It should be reaching out and adopting non-Taiwanese ideas and practices, not looking inward and searching the past for some sort of “Who am I” identity-crisis thing. By the time Taiwan people wake up from this wasted effort, the rest of the world will have passed it by, and Taiwan people will again know what it means to be an island nation, a third world country with once modern relics of its potential.