WWII Pacific is the scenario I have the least experience with... Why Japan? Isn't the US the strongest faction in this scenario, both in weapons as well as in production capacity?
But after I had France in the Napoleon scenario, I might be game for a more difficult challenge... I remember my last attempt was with the Common Wealth a few decades ago..., but I can't remember, whether I even finished that one, as it was dragging on very slowly...
Perhaps China might be an option, or would this be hopeless on Deity?