Romanization is, by and large, a thing that exists for people who already know European/Western languages.
Already done.
- Komen ça va? - Mo byin, mærsi.
We don't have anything against https://en.wikipedia.org/wiki/Louisiana_Creole, do we?
Romanization is an approximation that exists primarily for two purposes: 1. to express Japanese terms in other languages and 2. to enable typing Japanese on a computer. It’s silly to enforce kunrei-shiki, a system rarely used in practice, in the name of "accuracy" based on arbitrary criteria. Romanized spellings will never be accurate for obvious reasons.
Given the purpose of romanization, it’s more practical to choose a system that allows non-Japanese speakers to pronounce words more closely aligned with the correct pronunciation.
At some point you might as well use Roman characters the way the Cherokee alphabet does - which is to say, uses some of the shapes without paying attention to what sounds they made in English.
English is already heavily Norman-ized. Half of our vocabulary - including the word pronounce - comes from French.
I'd expect that Spanish, German and French speakers would benefit just as much as English speakers from these changes.
Use *h₂enǵʰ-ish please.
Obviously, being more transparent to English-readers is also a reasonable goal a romanization system might have, and if that's your goal the Hepburn is a better system. I don't have a strong opinion about which system the Japanese government should treat as official, and realistically neither one is going to go away. But it's simply not the case that Hepburn is a better romanization scheme for every purpose.
This actually happened in Vietnam, and Korea comes close although they use the Hangul script, not the Latin alphabet.
