Well, I felt there should be some sort of 'middle middle age' between the dark age and the renaissance. Feudal age, perhaps. Very important age
Unfortunately, in saying what I did above, I forgot entirely that this was on a world map (why did I forget that

). That changes a few things. You
do have to go by dates, as, for example, in 700 AD, in Europe it will be the dark ages and in mesoamerica it will be the equivelant of the european classical age. And will probably be different elsewhere as well. So when saying 'medieval age' that would be referring to the european medieval age, and whatever civilizations existed around the world at the same time, whether they be medieval or not.
So, I see two obvious approaches to organizing ages:
1) Base them on level of development (Ancient age - Classical Age - etc. Where even though different civilizations in different parts of the world may have reached these levels of development or ages at different times in history, It will all be in the same place on the tech tree)
2) Base them on dates ( Pick key date ranges in history, going back to my previous example, a ~300 AD to ~800 AD age. For someone playing the French, they would find that age full of dark age european techs, and someone playing the Mayans would find that age full of classical age Mesoamerican techs.
However, the first approach may work better for the game.
Anyway, I hope you don't mind me spouting off ideas. I know it's your mod, not mine. I'm just interested in the progress.