I have an idea:
Unions
How unions work? There is a small chance that if relations between 2 neighbouring countries are high enough, they can unite into one nation.
The name of a union can just be a hyphened mixture of both of the countries inside of the union.
Example: Jygop unites with Celtatia. This union will be called Jygop-Celtatia/Celtatia-Jygop.
Uniting with another country can increase the stability.
If you want to add anything else onto this, feel free.
You can tell me your opinion on this idea by replying. Thanks!