I am no where your level in Civ 3, but I have played WWII Pacific scenario a few times, though on lower levels. I think Japan is the strongest. The US has limited land and nowhere near the capital to capture. It also has its Forbidden Palace in Manila, which is likely to be captured quickly if you do not ensure it survives. Another disadvantage is that is starts without amphibious warfare (and the paratroopers tech, but I do not use them much). Japan starts with more land, and has the relatively weak China just next door to give it even more.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?
However, I expect it to be one of the easiest for you, as the AI is so bad at naval air war, and the deity production matters less as everyone starts with so many units.