"Fear leads to anger. Anger leads to hate. Hate leads to suffering." -Yoda
After watching several early access games where early warmongering was a thing I got to thinking about how one dimensional the warmonger hate system was in Civ V and largely still is in Civ VI. In Civ V all civ AIs despised war (except for the few civs that always went on the warpath themselves) to the point of skipping clear advantages and it felt flat. So far what I've seen in Civ VI warmonger hate is the same mechanic with only slight variations with the agenda system.
However, agendas are supposed to reflect a Civ's personality and define what they prefer in a given game. (Agendas seem to be more focused on having a standing military than actually using them.) But this doesn't create any realistic variety in how civs react to warmongering because of how static the base mechanic is. Instead of denouncing a larger more dangerous neighboring Civ the AI should consider the option of becoming friendly with that Civ while pushing it's own production into a prewar set up in case the friendship sours.
I'd like DLC or a mod that creates a warmonger fear mechanic in tandem to warmonger hate that directs the AI to change its focus to a defensive military state without denouncing a warmongering Civ. The effect could be created by generating the number from the hate mechanic without reductions from casus belli in relation to the potential for invasion. A Civ's fear could be found out through the espionage system to create a fuller picture of the state of inter-civ relations.
This way warmongering Civs will find that their neighbors are on to the threat they pose regardless of being denounced or their status of friendship. I've yet to see if denouncements in Civ VI are as near-permanent as they were in Civ V, but if they are anywhere close to it in Civ VI then there still needs to be more diversity in the diplomatic area of the game.