Love the idea of colonial/industrial, naval and trading conditions, not sure how the social one would work though, especially if you're a monarchist

"They should change the basic principle from conquering everything to something like what was mentioned above. Alliances should be somewhat more permanent. Instead of making alliances just to later break them, they should be more set in stone as time goes on."
Definitely Plaidwarrior, alliances need to be more tangible and sensible. Perhaps benefits for good behaviou/relations over timer, but definitely penalties for breaking alliances for no good reasons, other than just 'bad global reputation'...