Hepburn stuff:
Depending of the circumstances, long vovels are often signified by a macron. This leads to ambiguity since
ō can be either
oo or
ou, whithout further indication. I also believe that macrons are not usable in non-Unicode titles (since the German umlauts aren't accepted either), so we'll have to settle for a modified Hepburn version regardless.
You'll also have the discuss if you want to follow the
n-separation properly. Odds are, you've seen the word
renai in some titles before; that is technically not a real word, the correct spelling would actually be
ren'ai. Now, the question is if details like this even matter to non-speakers, since it only has very very minor influence on the actual pronounciation.
In terms of particles, only one has a truly decided romanization: は always becomes
wa. For the other ones, traditional Hepburn and the revised version disagree on the spelling. The traditional way uses the full romanization (
he,
wo), while the more modern one uses just the voiced part. However, every single textbook I've ever seen use romanizations used the traditional method, so take that for what it's worth. I'd also like to repeat that を (
wo) can make a slightly distinct sound from お (
o) depending on the speaker. This is magnified in songs, where more often than not,
wo is pronounced fully. There is absoultely no rule on ゐ/ヰ (
wi or
i), ゑ/ヱ (
we or
e) and non-particle を/ヲ (
wo or
o); even in modern Hepburn, you are free to use whichever you like. Personally, I favor the full form.
One more issue I have with Hepburn is that ぢ/ヂ and づ/ヅ are indistinguishable from じ/ジ and ず/ズ respectively. The romanizations for じ/ジ (
ji) and ず/ズ (
zu) are straightforward, but the other ones aren't. ぢ/ヂ are the "dakuten" form of ち/チ (
chi), which are
t-line kana.
t + dakuten results in a
d sound, so
dji would be a more proper romanization than
ji. Same story for づ/ヅ, which also originate from the
t-line and should thus be romanized as
dzu (as opposed to
zu). Some regional dialects make a distinction between these two sounds, so I strongly advise you to go with the longer, non-Hepburn variant.
The rule obviously does not adress my question concerning the handling of stylized katakana spellings and official translations of artist names, so that's another problem still.
Have you ever heard ヲタ read aloud?
I actually have, as you might guess it's pronounced mostly like
ota