New maps for MP and other concerns

[Postino]

i am curiuous since the campaign map uses a coordinate system to define battle maps, is it possible to define a new battle map by coordinates wihch are already on other MP players computers? this would do away with mappacks if possible.

also, are the files which MP checks for "creative unit adjustment" known? i would like to mod some campaign aspects without having to restore the origional files for MP.