There's also the thing that the editor would have to have plenty of potentially advanced stuff inkscape is already doing.
How about using noise filters to generate random interesting shapes on patches of grass, sand, and other nature layers of terrain? I myself certainly would like a feature like that in the map editor, so that I wouldn't have to hand draw everything on the terrain in the editor. Inkscape does this already.
How about making road area editing possible with bezier paths (with adjustable width), and (adjustable) rounded rectangles for parking lots, or why not any filled polygon shape? Of course, these would need to be editable, instead of getting burned on the terrain layer texture while editing the map. That alone is plenty of work.
Now, hypothetically, if the editor would be capable of doing everything inkscape is doing for us and all the possible convenience features so that certain things could be done more quickly than in inkscape now, with live 3D preview rendering, learning to use the editor from scratch would again be a huge investment for anyone.
This brings us to the question of how about making a simplistic map editor? We would not be using that ourselves for the most part, as you wouldn't be able to design unique bases with that. Maybe you could only pick bases from a library and put them on the map and draw the terrain layers with mspaint-like interface. Note, I'm not really suggesting this, I don't think anyone would like to use this either, as it wouldn't be deep enough for modders, and it would still be too deep for players with having to create terrain layers.
My assumption is that players would like an editor where they can get the map done in max 2min time. Modders are prepared to spend more time on the map than that, but I'm sure modders would like to have that 3d view to the game while they are editing the map, AND, they'd preferably know the basics of inkscape, or at least the difference between vector and raster image editing.
For modders, 3d "live" view to the game is already partially possible, you can launch RWR into a mode where you're alone in the map and the area surrounding you can be reloaded in a reasonable time, makes fine tuning a lot easier. This is not really suitable for working with terrain layers and height map, as 1) inkscape spends so much time exporting the layers and 2) heightmap can't be reloaded in the terrain scene manager without complete map reload.
For the players, the 2min map editing I could see happen like this: height map and terrain layers (excluding roads) are randomly generated with a click, second click re-generates them, there might be presets for forest, desert, island maps. You have a library of bases, which you can drag & drop to the map in front of you. When clicking on done-button, the road terrain layer is generated by connecting bases with random curved roads. Done, less than 2 minutes to create a map!
