Something I must try myself and there are quite a few hotseat campaigns running on twcenter if you have alook there. The real way to improve diplomacy in Med2 is to run a hotseat campaign with real people. That game is very schizoid in relation to diplomacy ( though better when using the Alexander.exe over Rome.exe or BI.exe especially in mods as that is very similar to what they programmed in Med 2/Kingdoms. Which is an enourmous improvement over Rome 1 which didn't give you any feedback.
It helps you get feed back in regards to what the ai thinks in the screen. Though diplomacy is much better in Med 2 to manipulate if you know what you are doing. There's an inbuilt malus to diplomatic relations related to each territory you take. The diplomacy is flawed at higher at campaign difficulties.
