I think we should have an option of where other rulers (particularly neighbours) pay tribute to you in the form of gold while they are still independent. I thought this could be done through the diplomacy menu of where 2 options would say “Receive a tribute” or “Send a tribute” to the ruler. This tribute is like receiving or sending a very large gift except this “protection fee” could last for 5 years for example.

To make someone pay tribute to you will depend on your power and their ability to pay you a large amount of gold when you ask for it.

This tribute is basically a protection fee to stop other powerful rulers or neighbours from attacking them for as long as the gold is paid once every 5 years. Paying tribute to enemies did happen historically to realms such as Novgorod paying tribute to the Golden horde, until they got more powerful than them by the 15 century and refused to pay them anymore tribute. While the Emirate of Granada was paying tribute to the Kingdom of Castille until 1492 when they ran out of funds and refused to pay them.

Also I realized this could work well with those rulers who are surrounded and outnumbered by other rulers of a different religion as well since they can pay a “protection fee” to all of them (as long as they have the gold) for 5 years to stop them from attacking them for a while.