Oh wow. I am literally slowly working on something like this as well. But my knowledge of mapping technology is very limited. My focus was actually much more o

Oh wow. I am literally slowly working on something like this as well. But my knowledge of mapping technology is very limited. My focus was actually much more on trying to use partly public data, and partly contributed data in order to 'render' information on top of such a map. My vision was basically to have all historically known people and there locations being visible on the map. Wikidata already has a nice start to this, but you would need a contributor model to flesh this idea out quite a bit more. Another step after that would be the movement of armies. This could be really interesting if you could see armies moving around at different times and getting closer to each other, or pass each other by. City population is another interesting thing. There is no easy way today to get a good estimate of what some city X population might have been at any particular period. That information is buried in all all over the place. There are many more ideas, but having his historical map is actually awesome for me, because that was the part that I know least about. So it should be an amazing piece of the puzzle. I will defiantly try to contribute to effort.