Late coming into this, but one question, why is the eastern edge of the map so bare? The eastern portion could be either turned into a Polynesia-like region consisting of numerous independent islands vying for power against larger multi-island kingdoms as well as both against outside colonizing forces, or it could be a larger continent that acts as a weaker counterbalance to the western powers, perhaps adjoined in culture to the long continent with the north-south axis, or as an in-between with a series of large islands vying for power in a sort of Polynesia meets very blown up Hausa city states.
As for the time period, why are we so intent on being in the early 20th century? Personally, I owuld think something earlier would be more fun. My favorite would be colonial (17th century), but anytime from the 17th-19th centuries is good.
On yet another note, I would say that I like the proposed idea where, in order to bring the timeline up to where we actually start, each person take a different region or group of people and develop from there. Of course there would have to be people (ie das) working to make everything blend together (especially with people like Genghis Khan and Alexander the Great coming along), but it would probably end up a much more vibrant and exciting world with people much more interested in their stroies if such a system for writing the timeline were implemented.