@IKael
I'd like to know more about the casus belli system you have in mind.
If we just earn points towards declaring war with reduced penalty because the game thinks we are justified to do so, it will be abused and manipulated unless the system itself is rock solid and hard abuse. That is hard to do.
I have something along with this on my mind:
A cassus belli system will be related to the public opinon that your civilization has towards another. The more favourable your public opinion is, the harder will be to wage war against that particular opponent. And conversel
Actions that would increase public opinion:
- Liberating your cities
- Waging war against a common enemy
- Been in peace for a long time
- Declarations of friendship
- Sharing the same goverments / civic / ideology
- Sharing the same religion
- Trading with you
- Keeping your word (even with a third civilization)
- Adopting your culture / religion
- Giving gifts
Actions that would decrease public opinion:
- Waging wars of agression
- Declaration of rivalry
- Waging war against an ally or against a civ that your public opinion likes
- Sharing a border
- Closing off their borders
- Rejecting your culture / religion
- Adopting a different goverment / civic / ideology
- Lifting trade embargos
- Razing cities
- Backstabbing other civs
- Persecuting your religion
- Making your spies succcessfully carry on a "fabricate cassus belli" mission
Note: You cannot do either declarations of friendship nor rivalry while in war against the "declared" civilization. Your number, frequency and effectivity of your declarations towards other empires might vary according to your techs, wonders and goverments.
The levels and effects of the public opinion would be then as it follows (from best to worst public opinion):
Brotherhood:
+50% to the effectivity of your science treaties with this civilization
+50% to your cultural influence toward this civilization
+50% trade route yields with this civilization
+75% war weariness if fighting against this civilization
-50% spyionage effectivity against this civilization
-30% strenght if fighting against this civilization
Affection:
+25% to the effectivity of your science treaties with this civilization
+25% to your cultural influence toward this civilization
+25% to the yields of trade routes with this civilization
+50% war weariness if fighting against this civilization
-25% spyionage effectivity against this civilization
-15% strenght if fighting against this civilization
Sympathy:
You might initiate science treaties with this civilization
+25% war weariness if fighting against this civilization
Indifference: No discernible effect
Antipathy:
-25% to the yields of trade routes with this civilization
+25% of spyionage effectivity towards this civilization
Disgust:
-50% to the yields of trade routes with this civilization
-25% to your cultural influence towards this civilization
-25% war weariness in case of open warfare
+50% of spyionage effectivity towards this civilization
+15% of strenght against this civilization's units
Burning Hate:
You cannot stablish trade routes with this civilization
You cannot sue for any other type of peace other than total surrendering with this civ
-50% to your cultural influence towards this civilization
-50% war weariness in case of open warfare
+75% of spyionage effectivity towards this civilization
+30% of strenght against this civilization's units