Spaces have been tried in Japanese. If you look at pure-kana (hiragana/katakana) texts aimed at grade schoolers and foreign language learners, there are spaces because without them there would be too much parsing ambiguity. Text with full kanji for adults do not use spaces, and this does not hurt comprehension at all.
> If you look at pure-kana (hiragana/katakana) texts aimed at grade schoolers and foreign language learners, there are spaces because without them there would be too much parsing ambiguity.
This cannot actually be true; the spoken sentences do not indicate word breaks, but grade schoolers (and toddlers) can parse them just fine.
Because there are accents in spoken sentences. Now if you would include accent marks in the letters it might make it easier to parse. Sadly, as far as I know there are no standard accent marks for kana.
While the prosodic contour of a sentence does help in parsing, there's a reason no writing system has ever taken notice of it. It's not necessary.
The most obvious way to see this would be to think about synthesized speech, which almost never uses natural prosody. Think of the voice of Stephen Hawking, or just a splicing of some prerecorded options. ("At the tone, the time will be / TWO / TWENTY / THREE / and / TEN / seconds.")
