From: Vermont, USA
If the landmasses on the planet map for the ground combat don't match the ones on the planet itself viewed from space. Like if it is obvious that they are totally different and unrelated pictures. At this point, maybe it is time to rethink the static graphics for planets and texturize them using 3-d meshes. The final image will still be 2d of course, but programatically generated. And then whether viewed as mercator, equalrectangular, or 3-d hemispherical projection, you will still use the same base texture map and it will still look like the same planet.
The map for ground combat is representative of the planet type and there is variety, but it is not an exact match for the globe floating in space. Frankly we didn't see the strong need for that as this is a representation rather than a map you move around on. The effects of the planetary terrain are factored into the combat resolution, but this is not a mini-game where the rest of the game stops while you move guys around. In that case, it would make more sense to me. Other than that, it would just be for art variety.
Please say you are doing this. Because it is totally doable. We did it on my old project (a weather map that used the same tile images but rendered for polar-stereographic, mercator, and 3-d globe views) and none of us were math-whizzes.
We're iterating towards a release candidate now, so I don't expect we'll completely redo a substantial portion of the art. We are doing another pass on the ground combat screen though and we'll improve it as much as we can, but we need to work within the realm of diminishing returns and what will keep us on track for a reasonable release timeframe.