This is the list so far (by country and then in date order)
CENTRAL POWERS
Austria-Hungary
Death of Franz Joseph, Hotzendorf dismissed and the new Emperor Charles I takes command of the Austrian forces (December 1916). A-H morale -5
Details of secret peace overture by Charles I leaked by the French (April 1918) Foreign minister Czernin resigns! A-H morale -5
Chrysanthemum Revolution (October 1918) Formation of Hungarian Democratic Republic led by Karolyi. A-H morale -20
Bulgaria
None as yet
Germany
German isolation!! Underwater cables to the USA cut (August 1914) German morale -2
Battle of Coronel (November 1914) German morale +2, Britain morale -2
Loss of Tsingtao!! (November 1914) German morale -2, Britain morale +2
Deutschland merchant submarine breaks Entente blockade and arrives in America!! (July 1916) German morale +2
Von Falkenhayn displaced by Hindenburg and Ludendorf (August 1916) German morale +2
“Turnip winter” in Germany (Winter 1916-17) German morale -5
German peace initiative fails!! (December 1916) German morale -2
Food rationing introduced (1917) German morale -5
Lettow-Vorbeck victorious at Mahiwa in German East Africa (October 1917) German morale +2
Mitteleuropa!! Client Kingdom of Poland established!! (November 1917) Poland becomes an ally of the Central Powers.
Treaty of Brest Litovsk (March 1918) Russia surrenders to Germany German morale +10 Annexations of territory including the Ukraine.
German Revolution (October 1918) Kaiser abdicates and Germany surrenders!
Turkey
Armenian massacres begin!! (April 1915) Loss of manpower for Turkey, up to 1 million Armenians may have perished in the genocide (obvious parallels with Nazi holocaust so may not be desirable to include this in the game). The Russians did manage to protect some Armenians so maybe they could get an extra unit in the Caucasus should this event occur.
ENTENTE
Arabia
Lawrence of Arabia joins the Arab forces (October 1916) Arab morale +5.
Britain
Battle of the Falklands (December 1914) British morale +2, German morale -2
Senussi Revolt in Libya!! (November 1915) Similar to Arabian revolt, but smaller, would need new units.
Conscription introduced!! (January 1916) Social unrest and strikes increase. Britain morale -5
Easter Rising in Ireland crushed!! (April 1916) British morale +2
Death of Lord Kitchener at sea!! (June 1916) British morale -2
Lloyd George replaces Asquith as Prime Minister (December 1916) British morale +2
Balfour Declaration (November 1917) next British unit recruited must be placed at Cairo
France
Foch declared C-in-C of Allied forces at Rapallo Conference (November 1917) French morale +5
Portugal
It seems quite possible to me that Portugal could have stayed neutral (for longer, anyway) in WW1. There was severe political instability between 1910 and 1920, including a short civil war at the end of the decade. There were two periods of dictatorship during the war itself (January to May 1915 and December 1917 to December 1918). In real life, Germany declared war on Portugal after Portugal interned a number of German ships at Lisbon after being requested to do so by the British. If they had refused this request then they could have remained neutral. Perhaps there should be a 25% chance of this happening?
Romania
None as yet
Russia
Tsar Nicholas II takes command of Russian armed forces!! Russian morale -2
Assassination of Rasputin (December 1916) Russian morale +2
Lenin arrives in Petrograd (April 1917) Russian morale -5.
Kornilov coup fails!! Russian morale -10
USA
Black Tom explosion in New Jersey caused by German agents (Jily 1916) Increases likelihood of USA joining the war
Zimmerman Telegram decoded!! (January 1917) Increases likelihood of USA joining the war
Woodrow Wilson wins US Presidential election on an anti-war platform!! Decreases likelihood of USA joining the war
NEUTRAL POWERS
None as yet
ALL POWERS
Food Riots!! National morale -5. To affect Germany, Austro-Hungary and Russia from January 1916 onwards (could happen more than once).
If you have other things that might be considered then please post them and I will update this list

