Adding Terrain and Population can make the game a lot more fair and different ideologies and resources for different tiles in the game? adding Leaders and traits for those leaders as well as personal Unions + letting nations create fully fledges pacts accords / alliances. Adding savings can also help. Also different technologies as the games go on can give certain nations with more resources having an advantage. TlL;DR: Add Terrain , Personal Unions , Population , Resources , Technologies Bigger Alliances , and Leader Traits.