...On Nexus I have found this mod "DIPLOMACY REWORKED" and going to forum messages the 3rd on this list said:...mod for diplomacy?1.5.4
Try this, for anyone interested. It works with e1.5.4 Main pretty good!
https://github.com/Jirow13/DiplomacyFixes/blob/1.5.4-beta/DiplomacyFixes-1.5.4-beta.zip
...haven't try if it works so you need to test it...
Source: https://forums.nexusmods.com/index.php?showtopic=8585338/#entry87279688