Why shouldn`t there be colonys, which can become independent after a time? For example you settle down on a new continent. The new continent is far away from the mother country, and there are living many barbarian tribes, which the player civilizes with weapons or with culture! If the "civilized" barbarians are more than the settlers(percentage), they can become(ex.: 100 years later or more) independent from the mothercountry and if they win the war they become independent. The new conutry should take a minor role, and should not be a protagonist civ! If you, the player, have a colony and there is an uprising(partisans, rebels, freedom fighters) you have the ability to let the freedom-fighters win the war without fight, or you must kill them in "set in advanced" turns(Sorry my english is not good, I hope you understand me). If you loose the country gets free! With minor role, I mean that this country has not the ability to change something or to begin wars(but you can conquer them another time and then they have an other status, notlike a colony but like a conquered country)This countries only exists and can make "minor diplomacy"(trade, change maps, right of passage etc.) they can`t use the full ability of diplomacy. They can build an army, but only for defend, the can earn money with trade, make alliances with other former colonies, etc. And there should be an further ability; Only one country(of the protagonist countries, not former colonies) can make a special diplomatic contract; To be a "protecting power" for the country. The protecting power earns 40% of the Income of this country and has the ability to move their soldiers in ttheir cities, without conquering them! You can use this ability for your interests

! I know, that I can write more to this theme, but it will last to long, so if you have questions´, ask.
Ther should also be this kind of Shism, which was in Civ1, and then was removed(Why?)