> I'm sure people have tried to come up with something, somewhere.
Perhaps related is the abjad used in Arabic and Farsi. Vowels are written with diacritics above or below the main part of the character, which represents a consonant. However, in modern Arabic, the vowels are rarely written and are inferred from context.
The bigger problem for Japanese is the absence of spacing between words. Even if you write everything in hiragana with spacing, it's significantly slower to read than when kanji is present without spacing. The mixing of kana and kanji usually provides a hint as to where word boundaries are, because there are few cases where kana is followed by kanji in the same word (eg お and ご), and kana which follows the kanji are most often a continuation of the word (okurigana) or a particle. Some words are usually written in kana despite having kanji available, and their presence can sometimes make it more difficult to read because they might look ambiguous with a particle or okurigana, and you have to figure out from context what was intended, which slows down reading slightly.
Perhaps related is the abjad used in Arabic and Farsi. Vowels are written with diacritics above or below the main part of the character, which represents a consonant. However, in modern Arabic, the vowels are rarely written and are inferred from context.
The bigger problem for Japanese is the absence of spacing between words. Even if you write everything in hiragana with spacing, it's significantly slower to read than when kanji is present without spacing. The mixing of kana and kanji usually provides a hint as to where word boundaries are, because there are few cases where kana is followed by kanji in the same word (eg お and ご), and kana which follows the kanji are most often a continuation of the word (okurigana) or a particle. Some words are usually written in kana despite having kanji available, and their presence can sometimes make it more difficult to read because they might look ambiguous with a particle or okurigana, and you have to figure out from context what was intended, which slows down reading slightly.