And i think for the AI single player version, make it like The ilian player suffer some diplomatic penalties but not everyone declare war right away, i think 2 things
1) If the Ilians are played by a human player, make the penalty a -4 vs ALL the other AIs and another -2 after another 60 normal turns for a total of -6 (which is not major but dont expect the AI to be very friendly with you, and as Ilians you dont really care about AI since you wont win a diplomatic victory as Auric anyways. Of course the - amount may be scaled with difficulty, like settler -1 with another -1 after 60 normal turns (these as scalled appropriately with different game speeds), warlord -2 with -1, noble -3 with -1, prince -4 with -1, monarch -4 with -1, emperor+ -4 with -2.
This wont mean much and consider that you as the ilians already have SUPERIOR production capability given the fact that SNOW = Grassland for you so while you thrive, everyone else suffers. and you can turn tundra into snow by building the temple of the hand ( i guess... not sure) so you have a huge lead ahead. Tundra is a puny +1(food) for everyone but since you can get snow, it's automatically +2food for you + you can build an improvement over it, with tundra all you can build is a lumbermill.
and 2) IF the AI is ilians give it a less of a penalty because AI is stupid, something like max -2 with -1 after 60 normal turns.
That would prove interesting.