In the last 12 months I recall 2 discussions in this forum on creating new versions of the 1939 25-player historical map ...
1) A June 1941 version at the time of Germany's Operation Barbarossa.
2) A December 1941 version at the time of the Japanese attack on Pearl Harbor.
I tend to favor the December 1941 version. You could have 3 pre-determined alliances as in 1944 Endgame map. One would be Axis powers (Germany, Japan, Italy, Romania, Manchuria). Another one would be Comintern (Russia, Xinjiang, Mongolia, Communist China, and perhaps Peru). And the last one would be the western allies (US, UK, Nationalist China, India, Canada or Australia). All other countries would be AI nations ... 