While I'm very interested in the Medieval and Ancient periods, I would love to see someone throw history to the wind and mod their own world. It would be a parallel Earth, with its own unique geography, culture, history, heroes, etc... (No need to alter the units, aside from changing their names and assigning them to appropriate new factions).

The First Age mod kind of follows this premise (then again, politics and economics in Middle Earth is boring and 2D; there's really only 2 alliances and that's it).

I'd like to starting modding the campaign map and go from there. I encourage everyone to take a break from intense historical detail, and just go super-creative! Make a unique world. :)