I've come to a conclusion about the guilds aspect: It's inelegant. I installed an inventors guild, a surgeon's guild, etc. and I believe I've just bogged down gameplay in the middle eras for minimal benefit.
I've added a three new wonders and the new leaders, and rebalanced things. I think it it plays very well right now, and I'm afraid that throwing in the hero units and guild buildings is just complicating what is otherwise a fun game right now.
The new wonders are the National Wonder Naval Academy, and Great Wonders CN Tower and Theatre of Dionysus. There are also three new resources: Pearls, Shellfish and Plays. 7 play resources are available to the one who constructs the theatre of Dionysus and it has bonus happiness if you have a theatre in your city. The Shellfish are Clams renamed with new artwork, but function the same. Pearls are a second luxury resource from the ocean, one found in warmer waters, unlike Whales, and give a lot of gold when worked. They use the artwork from the Clams, that's why Clams got changed to shellfish.
So I think I'll just concentrate on touching up the civs, and then that's all!