i also think you should add the east coast of usa, canada, brazil and argentina. they were growing into relatively strong powers during this timeframe and could make politics in games more enjoyable
Looks cool. But I think you should remain with the idea here, no need to add countries like brazil or argentina, that's overcomplicating things. And adding the US unbalances the games for the entente since the country just joined late in the war and didn't have much influence in the outcome of it anyways.
I think to simulate the USA and how it entered late you should have a line of territories from France/UK that you take and then finally get to a big bonus. But make every territory worth 1 or 0 so the creator can decide how long he wants it to be until aid is achieved.
I decided to not include any mini-maps, considering that neither Marne, nor Verdun or Somme were the most bloody operation in the war, but the Brusilov Offensive instead.
though not big in the war, siam/thailand was indeed a combatant of ww1 and shouldnt be kept neutral. maybe give them smaller bonuses to balance out, but they shouldnt be entirely neutral