Thanks for the list, Durian!
Among these sites, the strongest candidates are probably Kanazawa, Zenkoji, the Shikoku Pilgrimage, and Usa, Kunisaki, but that's probably because the historical and cultural values of these sites are immediately apparent. I wish there was more information on the other potential nominations: what sites are included, what is the rationale, etc.
Like Hikone Castle, I don't think Matsumoto Castle is alone sufficient for inscription. A better option would be to put forward a serial nomination, such as Medieval Castle Architecture in Japan. Out of the 12 castles dating to at least the Edo period, several medieval examples are still extant. Also, the Nakasendo nomination would definitely be stronger with the inclusion of Narai, considering it's historically more important than Magome and Tsumago.
Speaking of Hikone Castle, which is on the tentative list, I really do not understand why there are no attempts to put forward the Lake Biwa Cultural Landscape as a nomination. Not only would this include the castle, other important historical and natural sites in the encompassing area would push this toward inscription. In addition, Ise Grand Shrine, Japan's most important Shinto shrine and a surefire candidate for world heritage status, continues to be missing. I really cannot fathom the thinking behind Japan's candidates.
Anyway, in spite of its ICOMOS evaluation, I would like to see Kamakura installed on the list eventually. The candidature file was simply mishandled. It would also be nice to see the Amami Islands soon show up, along with a Japanese Tea Cultural Landscape or Japanese Gardens nomination, sometime in the future.