But... what if the Marshmellow Queen wants to MARRY King Edward Longshanks?

[quote]Identify 3 starting areas on the map, allowing players to pick either of those three. Categorise the starting areas as: "Westernised" (Roman/Greek/Egyptian like cultures), "Easternised" to cover the more outlandish nations that reflect the likes of India and China, and then an "Exotic" area, where literally anything goes. [/quote]

That's not a bad thought. But it means splitting your playerbase into three groups, limiting interaction between them. I dunno. This is a hard problem to tackle.

One thing that might be important to ask is this: what are the origins of the different species and cultures on this planet? Was everything born on this planet naturally? Are you going for a traditional fantasy background? Or is there maybe a splash of science-fiction in this planet's history?

Personally, I'm not against the idea of distinct cultures slowly homogenizing, but you'd have to enforce that somehow. That'd be the problem.