This was WAY harder than I thought. My own rules making it so much harder on myself than I needed to be. I never saw any late-game emergence. I've left it on overnight with different bots and different setups and basically been simulating one thing or another for about 2 weeks straight and I never saw any later-game emergence. Not saying it can't happen, but generally after thousands of generations, I've just gotten stuck in a rut.
The good news is, I didn't have to run these very long. I was able to get a nice satisfying video in 120 generations, or about 22 minutes. Not long term, but solved most of my criteria!
Enjoy!