ShadowWarrior, you nailed it in my opinion. Right now, if someone threatening is on your borders, the only thing you can do is either build up your defences on that border, or form a pre-emptive strike. ... let alone paying them off and hoping they keep their word.
First off, I would have many small non-competitive nations, who play historically but not ruthlessly. Only a handful of nations would be competitive enough to never trust you, or to abuse your trust. (see here --
http://forums.civfanatics.com/showpost.php?p=2100214&postcount=127 -- for details)
With that, you could open up new strategies for dealing with nations. Strategies that make you more powerful and not necessarily larger. Strategies that can be accomplished with zero use of force, in complement to force, or in spite of force:
1. Culture your rival
- send missionaries, artists and philosophers to make their people bigger fans of you --> more of your culture within their borders
- trade with them, to make them lovers of your luxuries --> more of your culture in their borders
- have an overall astonishing culture, increasing the value of your culture
Conclusion: With their people bigger fans of you -- more of your culture within their borders -- they feel more akin to you. The people experience more war weariness against you, and even the troops have lower morale. With enough cultural similarity/superiority, the entire nation could be absorbed into your empire, even if just one city at a time.
Examples: (Nations that cultured a rival into peace) The Northern Europeans culturing (Christianizing) the Vikings, China culturing the Hans
Examples: (Borders expanded through cultural hegemony and similarity) The spread of Islam (in the non-violent cases),
2. Make them economic dependants
- there's an expression: if Britain sneezes, Argentina catches pneumonia
- make resources more meaningful by making them useful even in buildings and everyday life
- model scarcity and supply of resources
- have the ability to leverage your resources -- be their only supplier of oil
- have the ability to take someone technologically inferior, buy out their resources, refine them (lumber --> furniture, oil --> gas), and sell it back to them!
- have a geographic position such that all trade routes go through you, and allow you to be a third party in said negotiations to demand a small payment for using your roads / harbors
- having a huge population makes you a huge market, and thus huge potential for profit, particularly if those people are demanding world famous products
Conclusion: Nobody's gonna bite the hand that feeds them. Unless getting fed becomes too scarce or too costly, in which case they'll bite in hopes of having direct access to the food supply. This would be the ultimate way to prevent war -- you won't see Britain and France going to war anytime soon, not until some resource starts running out, or one of them starts being a bad businessman. And if trade becomes open enough, you could take them in as a colony, or unite as equal states.
Examples: (Nations that were once rivals but have too much at stake to not be close to one another) -- Canada and USA (19th century), the European Union (20th century), even tense relations between China and the Western World (21st century)
3. Have very common goals, enough to vassalize them or annex them, or just make them need you
- basically, for a high enough price, an AI nation will surrender completely
- particularly early on in the game, throwing down 100 gold could buy you the "surrender" of an AI with one city
- more cultural similarity, economic dependence, technological superiority would make it possible to buy them for cheaper
- happens under the gun -- if they're threatened by someone, they beg to become a province
- happens particularly under YOUR gun -- if there's no hope in hell of winning, might as well accept colony status before war breaks out
Conclusion: Nations are vassalized all the time. This is how empires are built, even unofficial ones. Particularly in the case of AI, factors like cultural similarity and economic interdependance can make the people of that nation more ready to accept membership into your glorious empire, all without firing a single shot.
Examples: Britain colonizing India (Age of Discovery), the Franks and Goths squashing their beef in the face of Islam (Dark Ages), Italian city-states joining the Franks for protection from one another (Middle Ages)