I think you make a very good point, although I really think you could put your argument together better.
Mandatory might be going overboard, but I always thought that there should be a CHOICE on which language to learn in schools. Seriously, English isn't the only worthwhile language to learn and Chinese is way up there. It's not like they do a good job of teaching English anyway!
I took Chinese in Japan for about a year. The Japanese students seemed to treat it almost as a form of "Spanish" to our English. Sorry if that comparison isn't exactly helpful, but with the kanji already existing, similarities and such helped them gain a quick understanding of the sentences and words...
Only problem is their pronunciation was just AWFUL and they didn't seem to have a clue how to say anything correctly. The concept of correct pronunciation seems to be very absent... I took basic Korean too. Korean in Katakan that is... at a university level. F'ing pathetic and I rolled my eyes when I figured out that it wasn't the Hangul that most students were reading, it was the katakana on the right page of the dialog! Of course I had my own problems understanding the book explanations, but while in Japanese they were better than most English books.
Yes, I think there is a strong case for learning Chinese. However, Japan's language study and teaching sector has a long way to go.