I love the idea of my plans for post-war Japan. I largely focused on the social engineering aspect, but I can try again.
In my short ideas (which I'm working into Age of Legends, but I have a nasty case of no-idea-where-to-begin on that one), had Japan taking their WWII defeat hard, and the Americans making more of an effort in rebuilding Japan. Japan pre-WWII takes in the Jewish immigrants that Europe doesn't want (good deal for Hitler, in many respects), and results in ~500,000 Jews in Manchuria, who were staunchly pro-Japan (if they saved me from the gas chambers I would be too) and fight like mad, which along with the Koreans and Chinese who actually worked with Japan, help them accept that after WWII their racism is not only unfounded, it's holding them back. Like Meiji thought, the best way to advance Japan is to get the skills and people to make the country better.
Japan post-war stays relatively isolated, but as Japan grows into an economic power in the 1960s and 1970s their immigration doors open, starting with the Nikkeijin and the other South Americans, Jews (mostly disenchanted Israelis in many cases), Koreans, Filipinos and a handful of whites, mostly Australian and Americans. Japan's boom economy in the 1980s turns this flow into a big river, which is how Japan not only becomes an industrial power but also a cultural one - Tokyo along with Mumbai and Los Angeles are the world's film capitals. Japan by 2000 is home to some 165 million, has a $6 Trillion economy and is considered one of the world's most dynamic nations.
Now, this Japan, minus Article 9, would have a massive navy - not USN size, but bigger than anybody else by miles, even well beyond the RN or the Soviet Navy - simply out of need to protect its shipping lanes and citizens abroad. With Japan being so close to the PRC, one of the needs would be to have some power projection, but mostly the Japanese would be focused on homeland security, which means a huge fleet of destroyers, frigates and submarines, both SSN and SSK. I'm thinking that the Japanese Navy has a few big cruisers to act as destroyer leaders and flagships (I'm thinking something like the American USS Long Beach here), but their navy will be primarily based on defense and protection of its shipping routes.