So I managed to get vassalized by Red. Played until turn Turn 82 where I got to pick the Aztecs after getting two free people to assimilate with me.
I am not sure where to go from here and sadly don't have enough time to play out certain styles to meet the challenge.
It is genuinely intriguing set-up to play out. I will, hopefully, eventually.

Anyhow, here is the screenshot and save. Turningpoint.ctr