[Captain Kwok]

The main modifier I think has the most effect on diplomacy is the categorization of each empire. There are 3: Peaceful, neutral, and aggressive. Each adds various modifiers in the AI scripts for diplomacy. The friendly AIs like the Phong or EEE come around first, while the others require an improvement to their mood before they will interact in "positive" terms. Overall the behaviour isn't working out too badly, with the exception of the random treaty elements.