I just found The trick! *dances*

Easy like heck. It's exactly the opposite of a Shadow Mapping Shader. You just let the Map Compiler shade the geometry as usual, and then remove the shading in realtime with a simple material!

If someone is interested, this is the workflow:

-Model geometry in your favorite 3d app, then bake the shadows and textures at will (in a single skin, usually).
-Import in WED. Add lights (*SEE BELOW) and set the mesh as SHADED (not FLAT).
-Let WED create the lightmaps as usual. WED will generate a second entSkin to store the shadows of the mesh.

-Assign a little material to the meshes so it doesn't render the shadows!

This is the most simple material. The only thing it does is to 'paint' the mesh with its own skin, ignoring the shadowmap skin. So, basically your mesh will look exactly as FLAT shaded (showing only the beautiful baked shadows), but the lightmaps will be still working, so the entities standing on it will still be lit correctly.

Code:
material mtl_nolightmap
{
effect=
	"
	
	texture entSkin1;

	technique nolightmap
	{
		pass p0
		{
		  Texture[0] = <entSkin1>;
		  			
	  	  ColorArg1[0] = Texture;
		  ColorOp[0] = AddSigned;
		  ColorArg2[0] = Current;
		}
	}
	";
}



Please forgive me because I never coded materials before, so I don't know if this is correct way to code it. I just stole scraps of code from other complex materials I found around. It works so far.

* About adding lights: You may have to manually recreate in WED the light positions you used in your modeling 3d app, so the lightmaps will correspond to the baked shadows. But the good news are that very soon we'll be able to import whole arbitrary 3D levels including lights:

http://www.conitec.net/beta/wed_import.htm