I'm playing my sixth country now - Italy and mention here a few design flaws that need attention for whenever the next update is considered:
Allies do not return everything. When a region rebels, as in Polish Russia, one of Russia's allies, either Prussia/Germany or Austria can enter, defeat the rebels and is supposed to return the region to its righful owner. It usually does for the region, but not the city in the region nor its production facilities. Playing Italy and so watching the AI play itself there, Austria wound up with Warsaw and its farms, surrounded by Russia. Sometimes they don't even return the region, as when Prussia defeated the rebels in Vilnius and kept everything. A variation on this is my next issue.
Major powers do not give up colonial cities when colonized by another. I've seen this several times. France in Tunisia, GB in Nigeria. They go to war against the natives, capture a city, Lagos or Tunis and do not give it up when another power creates a protectorate or colony, even if allied. The colonizer has 100% military control over the region and obviously sufficient CP to obtain a protectorate. The colonizer can build any colonial facility but cannot build a habor or railroad. The only way to change the ownership of the city is to go to war with the other power. This leads to another colonial issue.
By design, I guess, protectorates aren't really protectorates. The native armies are thrown out of the country, even into an unexplored region where they wither and die through attrition. It would be much more accurate if the player was able to take over native armies instead and keep them in-country. As for armies,
Allied forces prevent capture of a region. I've seen Russian armies spend more time visiting regions in Austria then they do staying in their own country, even though they are fighting the Crimean War sometimes for 40 years and Austria has no war. When one does go to war against a county with an ally roaming about, such as Russians in Austria, their presence in a region prevents the region's capture. When one brings overwhelming force agaist a weak opponent sufficient to easily destroy the garrison, the battle repeats every day of a turn against a new garrison, destroying it, until the turn ends and there is still no capture. Why, not because of the opponent but due to the presence of an allied army not at war with you.
I hope these and other issues are addressed for I believe the game has great potential.