Earth 1000 A.D.

I think the map isn't four times bigger, but maybe one and a half times. Filling it out... is quite possible, especially if I manage to create a good map in two days, plus two more days for improvements, then 12 days is a perfectly reasonable time to make a huge map. And if you try hard and have the patience, you can do it even faster.
Well, yes, of course, increasing the area without increasing the number of players is indeed pointless. But if both were possible, I would definitely play to my heart's content, and others could do whatever they want.