> I'm also not a fan of accented letters like 'ô', which in a romanization, inches closer to IPA territory.

Japanese has ten vowels ā, ē, ī, ō, ū, a, e, i, o, and u. If you delete the macron over the vowels, you just lost half of the vowels of Japanese. It would be like writing English without the silent e (e.g. mat, mate would both be spelt "mat") because silent e is "devoid of information" and "noise rather than signal."