I didn't put too much thought into this I'll admit but I've been considering a group of players with a rather unique tech base; none at all. In this group The Crusades exist along side the Napoleonic Wars, F-22s alongside Sopwith Camels. It's like a mirade of technical bases all managing to exist in the same world; sometimes peacefully sometimes not but there's one single rule. Even if you're the most advanced tech base in your regional area you have to be 'fair' and fight your enemy on their technological level.
Politics vary compared to region -and- time period of the area. One area might be 1900s Monarchy, another might be 2000s Democracy, another might be 3000s Technocracy.
Any ideas, NS?

