I propose a crisis mechanic but it should be player oriented meaning an action taken by player cause a tense and tough situation and also affecting diplomacy and some effects.

Situations can be like:

An agressive military expansion resulting in causing of wide scale alliance and forming ties.

It can also cause wide scale war.

In modern era there can be ideological tension between two major faction and causing alliance with same ideology and wide scale close border. Due to close border causing economic crisis and cold war relation with each other and cause skirmishes. There can be civs which are neutral to both side.

Due to some action causing unhappiness in people and causes terrorism in region.