Basic fractions diplomatic relations
Apart of the "case fire" operation you made the same apporeach like I did. I agree, it is very easy.
I get the idea that any fraction in the game has a kind of basic relations to any other fraction. No matter how they act during the game. For example:
WRE 'loves' the Franks, but will always try to bring down the Alamanni...
ERE hates the Goths. While playing the Goths they attacked me with no reason. When hording and only try to cross their lands they threated me and attacked. While starting a few ticks with the Vandals they allowed me to cross all ERE in europe without any word - until I attacked all their cities there at once!