I've come up with the idea that the Player Character will react to AI based on their agenda. The Player will receive bonus or minus relationship modifier as a result. For example, you as Frederick will irritates if Pericles befriends a city-state. Originally, you would forgive Pericles because the player might not be interested in befriending city-states. However, the agenda of Frederick will cause you to rival Pericles. But here come's the question, is there anything to lower AI's opinion by script? Lua doesn't have "Set Opinion Value" function. I suppose detecting agenda would be easier than that since most required functions are avaliable.