But I think that in order to get there, one would need a fairly early POD, say before 1916; after the Warlord Era began, the Japanese wrote off the Nationalist regime as not worth the bother, and figured that China's lack of a working central government would enable them to satellize it one chunk at a time, starting with Manchuria.
This is a really, really, really interesting idea, and one that I've toyed with in the past. But I can't see just how you get there.