I think it would be even more interesting if it were a 3v3 Axis vs. Allies map, with Germany, Italy and Japan vs. the British Empire, Soviet Union and United States. The problem, of course, is that the Allies have a significant advantage in that line-up. What made the real war hotly contested (and kept the outcome in doubt until 1944 or so) was that that Axis powers did not go to war against all of the "Allies" at the same time. Rather, Japan started tearing China apart in 1937, and Germany took down Poland in 1939, France and the Low Countries in 1940, and left Britain with little ground forces offensive punch. Of course, Hitler turned east and attacked the Soviet Union and the Japanese bombed Pearl Harbor in 1941, bringing the Soviet Union and United States into the war on the same side as the British. On paper, at least, the war was already over when that happened -- it was only a matter of time and competent generalship until Soviet manpower and American industrial output overwhelmed the Germans and then the Japanese.
If the Germans had finished off Britain in 1940-41 before attacking the Soviets, the Japanese don't attack the Americans, the United States doesn't enter the war, and -- presto! -- most of the world is speaking German and Japanese in 2017, including perhaps the United States, Canada and Australia.
How you incorporate that time line, and those contingencies, into a COW map is the question. And let's not forget that the Soviet Union was a wild card until the Germans attacked it in 1941; the Soviets could just as easily have become active wartime allies of the Germans under different circumstances . . . .
