Sorry, i don't think i made myself too clear.
I'm looking for a means to map a sky texture to a solid poly on the map geometry itself. This is where the quake comparison came from. When constructing a quake map rather than having an open ceiling or window exposing a sky box or the like you map the geometry with a "special" sky brush. By special I mean it isn't mapped like usual textures, it's mapped in such a way that it exposes a background/sky scene.
I'm looking for a means to map a sky texture to a solid poly on the map geometry itself. This is where the quake comparison came from. When constructing a quake map rather than having an open ceiling or window exposing a sky box or the like you map the geometry with a "special" sky brush. By special I mean it isn't mapped like usual textures, it's mapped in such a way that it exposes a background/sky scene.