I suggest minor state because independent people even got certain change they have to get merge or destroyed at last.

The things which differ them from Independent people can be:

I think that the minor state should have more than one territory.

These can be vassalized and allied.

These minor civ leader can be of 3 types democratic, autocratic and dictator.

In democratic minor civ the leader can change after some turns. The change can be avoided if leader approval is above 50%.

In autocratic minor civ leader change less frequently  and people approval does not matter.

In dictatorship leader will stay for unknown number of turns.

The autocratic or dictator can be brought from coup or revolution.

These can acquire nuclear weapon.

These can form in a way like independent people.

These minor civ can be battleground of major empires for influence.  

Two minor civs can merge and disintegrate.

They can have a leader but it will not be permanent and these leaders will come up with the set of thinking and traits. This can impact relations and we all can see that as the turns progress there  can be change in scenario because of change in leadership of these minor empires.

Leaders can be changed by spy mission like assassinate or attempting coup.

If minor state destabilize there can be danger of large rebellion which can attack neighbouring 

empires  and can disintegrate and form more new minor civs. 

Scenario can be colonization of unhabitated continent with these minor civs or a cold war scenario.