One more thing …
The opening turn would be a single round attack by the Japanese with a 5 damaging ships and a 4 or less killing a ship; and air and ground units are killed on a four or less. The Allies damage a ship on a 2 and kill a ship on a 1. Air and ground units are killed on a 1.
This is my starting thought on a first turn Japanese advantage.
Lets see if that can survive some play testing.