I like the concept but dont really agree with the implementation.
Civs shouldnt be able to declare a cold war instead the diplomacy, trade, and espionage systems should be massively improved so that they have far more influence on the game. If these systems are revamped so that trade embargoes, covert dirty tricks, and diplomatic blocs have more strategic importance; the game will throw up cold war style scenarios time and time again without anyone having to declare a state of cold war.
The will of a nations people should also play a greater strategic part in the game. The Soviet Union didnt simply collapse because of the economic strains of the arms race and of pressure imposed by the Western bloc (not only the U.S.) ultimately, it collapsed because the system had fundamental weaknesses and it failed to accommodate the wishes of its people.
The regime change idea could easily be implemented by having a Civ go into anarchy if it loses its capital city/ leader and that civ offers terms for a peace treaty. When a new government comes to power its relations with the occupying civ improve from furious to cordial (assuming that the peace treaty was agreed if not, war continues with the new government). This way its simple, straight forward, and easy to implement. Leaders could also be assassinated via espionage and if they are autocratic systems this would create an anarchy type state where the regime remains stable but suffers from an internal power struggle the lack of leadership at the top would create several turns of reduced productivity and trade and an inability to sign diplomatic agreements. Democracy & Republic would be immune from this because they can elect a new leader relatively easily and because increased freedoms mean that citizens are less reliant on the State for direction.
I like the idea of introducing crusades to Civ. Medieval Total War did a good job with this basically the mechanism worked by declaring a target area (i.e. a province occupied by either heretics, heathens, or pagans) as the target for the crusade. This target area had to be captured by an army of crusaders that could claim right of passage and recruit volunteers from rival factions that shared the same religion - the crusading army was also self supporting (very useful in a game where money problems were constant and serious). The down-sides were that the crusading army was unable to do anything else whatsoever until it had captured the target province and the army could also suffer desertion if you took too long in grabbing the land. This was a good system and it could easily be transferred over to Civ although I think that it should be restricted to specific regimes e.g. Monarchy, Feudalism, and (if its included) Fundamentalism. Rewards could include victory points, improved relations with nations that share your religion, and the creation of a military Great Leader when the objective is captured (if the objective city is sufficiently challenging not a town thats adjacent to your borders!)
I dont think a Commonwealth is workable in Civ the UK does not tell its former colonies and dominions what to do rather it is a system of amicable relationships between the various elements of the former Empire. This wouldnt work in Civ because there is no incentive to behave in this way it is yet another disparity between the game and the real world. Friendly diplomacy seems to have no role in Civ.
I think liberation should definitely be included in Civ 4 (there should be ways to play the good guy) rewards could include VPs, glory, improved international relations but further rewards could be the following:
1) The liberated Civ is your new best friend your reputation with this Civ is reset to the best possible setting (i.e. gracious) and the Civ will trade techs, resources etc with you on the fairest possible terms (although the Civ will not simply give things away the trades have to be FAIR not exploitative) in addition the Civ will never declare war/ ally against you and it will happily sign mutual protection pacts/right of passage agreements/military alliances with you. Of course you can ruin this happy situation if your subsequent actions include bullying/attacking/signing trade embargoes against this Civ.
2) The unit that liberates a Civs former capital will automatically create a military Great Leader.
3) Totally liberating another Civ will enable new construction options e.g. the creation of a small wonder called Heroic Sacrifice which would represent the numerous war memorials and graves that pay tribute to the many brave soldiers that suffered and died to save the occupied country. This wonder would generate lots of culture and would improve the solidarity of your Civ (assuming that Firaxis adopt the loyalty & regionalism concepts that appear in numerous other threads).
4) The liberating Civ would benefit from an Age of Glory e.g. double culture per turn for 20 turns.
Sorry about this post being so long ideas just kept springing to mind and before I knew it I had wrote an essay!
