It always bugs me how the ai pretty much seems to act as a single coordinated colony organism even if they hate each other.
Only two of the default races "hate" each other, Yor and Iconian. The rest of the races are not setup to have hated factions. I tweaked the "We will Conquer the Galaxy" Modifier so it has more of an impact on the AI. I would also add hated faction or factions to the rest of the default races, but, it make the game very warlike but I am unsure about this atm. It fits well for my Trek mod but I am not sure if the general player would prefer the galaxy be more dependent on war.
A typical example of how this impacts gameplay: My last test game, by turn 220, 2 factions had been killed off, each by a different AI, one AI ended up with 93 planets after their conquest and the other ended up with 88, each faction started with 35-45 planets. One AI had a 6 way war, which it was winning.