Extra wasteland/sea doesn't really slow the game down that much. Also, the northern stuff only takes up so much space because they're using something like a Mercator projection.
Alternatively, there's the approach they took with the EU3 map, which has a bit of a curve to it, but at least avoids any sudden misalignments.
The projection they use in EUIV is a modified Miller cyllindical, which again is a modified Mercator. Even though adding more wasteland and sea zones doesn't cause much slowdown, it takes away pixels from useful places, like Asia, rest of NA, SA, Europe and Africa, just to add wasteland in Canada. Why does people want smaller provinces elsewhere or a larger map (which uses more memory) just for that?
The EUIII map projection is very ugly, and I really hope they don't use that. Ever. The projection they use in EUIV is the same as in Victoria II and it is the same as they will use in HoI IV. It is here to stay for a while, and if they ever make a Victoria III, I hope they use the exact same map as in Victoria II, without the fancy graphics in EUIV and CKII. Victoria II is the best looking Paradox game, and adding stuff like heightmaps would break that.
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