Well, I have reduced the PSEUDOYIELD_CITY_DEFENDING_UNITS parameter, with further reducing during each era. I am still testing, but already noticed, that AI civilizations became more rigid in signing peace with each other (and with the player as well) In addition, AI is more active in moving troops towards enemy cities, BUT he often takes stupid losses, when he sends one or two units to the enemy territory, under the city ranged attack and so on. It is strange, because I did not change any tactical files of the mod. However, it's just my preliminary look and I still need do more testing.
And I have one more suggestion, if it wasn't done yet. Is it possible to make AI evaluate the diplomatic status of other discovered players? For example, when two players declare friendship or create alliance, other two become more likely to propose/accept friendship/alliance offers. You did very well with your strategy models, but it would be awesome to add some evaluations connected with diplomacy. It also would make diplomatic victory more difficult for the player.