I may not have shown it there, but actually the penalty for different allegiance increases over time. By the endgame there is simply no chance for peace across the lines of idealology.
If the AI ever becomes formidable, that could be a lot of fun.
By the way, can you change the diplomatic positive/negative statements that represent modifiers? I noticed you commenting on these in the video, and I agree. Quite a few are pretty opaque.
I am thinking about some new Realm Wonders that require large amounts of Influence to construct. I have already switched Merchantcross Bazaar to 100 Influence. I will probably have a production wonder, a shard wonder, and maybe a Citadel wonder for defense. Other than that aspect, I think the basic city differentiation is quite good. I don't want to add more complexity until I get the AI to use what we already have.
Truly high level wonders would be a nice strategic option to have available.