The BTS attempt at a Second World War mod was pretty awful in my opinion. Few diplo options, and the AI is just broken.
I played as the Soviet Union on Noble, and just spent ages building up my forces and destroying Finland, waiting for the Germans under "von Papen" to go crazy, attack Poland and destroy France etc.
I was waiting for a long time, it was 1941 when they finally attacked Poland.
Waited some more for them to break the non agression pact and destroy me, but by then I'd already gotten bored.
No simulation of the various pacts and agreements either.
Free play mode is awful :/