Expand the campaign map?

Is it possible to expand the campaign map? I'd like to fill in the empty space northeast of the Aral Sea & create the Huns.

No, it's impossible, I'm afraid. Map, from adding new regions to moving the capitals of the already existing ones, is unmoddable. The only exception is the renaming of cities and provinces, but that's all.
My only hope is that, there will suddenly appear a Russian ex machina, just like in Empire, where they added the Khanate of Khiva, but even in that mod, there were several bugs, unfortunately.