At the time of writing, the rules still aren't finalised, but realistically not much more will change as they go to final, absolute, no more messing about edit in preparation for layout in about six weeks time. It will read a bit more like a postmortem than a dev diary, for the simple reason that I didn't keep a dev diary. So I'm doing it from memory, and we've been working on Age of Tyrants on and off for seven years. I say on and off, because I've had two full time jobs and several other independent projects during that time. I offer that last bit of info by way of explanation for why the project has evolved and changed so much. As we spent time away from the project, it inevitably lead to re-evaluations and new ideas when we came back to it after our many hiatuses.
When it came to writing the background material, the troop descriptions, timeline stuff, and colour text I had a good head start. The Draconis Alba galaxy has been in development since the late 1990's, and I was involved back then in its original incarnation as Void.
John Robertson and I were working together on another project back in 2008, a 10mm scale fantasy system that has yet to see the light of day, but while we were working on that, we wondered what would happen if we applied a similar set of rules to the Urban War/Metropolis universe, and thus Age of Tyrants was born.