I think that some key values for IME are duplicated.
There are Hiragana, Katakana and RomanCharacters.
However, there are also JapaneseHiragana, JapaneseKatakana and JapaneseRomaji.
I think that "Japanese" prefix isn't necessary. So, I'd like to suggest that the latter names should be removed.
Updated in the latest editor's draft. Thanks!