In my opinion the game should run until December 31st, 1924, as it gives plenty of playing time, and allows the war to develop and its prospective results to manifest properly. Seeing as important events occurred in 1923, another year would allow these events to unfold in the game until the games conclusion at the end of 1924.
I agree that ‘bitter peace’ events are crucial – and that there should be events that simulate all the peace treaties, the collapse of Austria-Hungary etc.
The countries that emerged from the peace treaties should also be simulated: Czechoslovakia, Poland, Hungary, Austria, Yugoslavia and so on, using the tags from the standard HOI.
Essentially, there must be two sides to the coin, which is why I’d suggest some alternative peace treaties for the defeat of the Allied powers. Brest-Litovsk handled the Russians, and so how about a theoretical ‘Treaty of Berlin’ that puts German terms to the British and French or a ‘Treaty of Constantinople’ that puts Turkish terms before the allied powers?