1920s wouldn't be bad either. Apparently Hong Kong has had wave upon wave of refugees due to various invasions. Chinese refugees fled there when Japan invaded them, Vietnamese refugees fled there when they got invaded, there's British citizens left from the occupations, and every minor culture that got swept up between the waves. It goes way, way back and the island has been a refuge and mixing place for centuries with the World War II stuff just the most recent twist.
In a post 40s setting, because of all of the "western" influence and capitalist allowances, character types from the "normal" WoD games are present within the city state as well as the eastern spin off variations. It's alot like the Chicago setting for nWoD but much smaller and more varied. And since its in such a state of change through modern history, it isn't fully controlled by all power elders (like any place old in WoD tends to be) so fresh players can shake the city power structure.