>  The written-spoken language is very regular so it's very easy so "sound out" words.

I don't know where I stand on your thesis (I was mostly arguing against the idea that Japanese people are demotivated to read more than English speakers because of kanji), but the main reservation I have about this is that it's pretty easy to fake knowledge of words this way. The pronunciation of something is secondary to its definition. But with a phonetic language, it's easy to fool yourself as well as others of an understanding that is not very deep.

I remember once in middle school I elicited a laugh from my classmates when during group reading, I mispronounced "awry" (I had put the stress on the wrong syllable as well as pronounced the "y" as "ee"). However, I had a very good idea of what it meant at that time. OTOH, in that same class, it was a very unusual occurence for the teacher to interrupt group reading and confirm everyone knew what a word meant, so I believe many misunderstood words were glossed over routinely.

I'm not saying being phonetic is a net loss, of course, just that "understanding" is a tricky thing to gauge, and may be harder as a side effect of some language being phonetic.