Would a Japan comprised of the home islands, Taiwan, Korea, and the Philippines be internally wealthy enough to become a Superpower-level entity?
Let's say Germany got the Philippines and Japan grabbed the archipelago during the Great War.
Looking at these territories today, that's a population of about 330 million people. However, if one discounts deaths from WWII, the Korean War, emigration, and the North Korean famine the population could conceivably be 360-380 million people.
I'm thinking that if Japan gets the Philippines after the Great War, the navy will be the stronger branch of the military (meaning less army militarism) and the country won't feel deprived of gains from the war. Japan then spends the next several decades focusing on consolidating its gains rather than expanding.