Is it possible to put custom battlemaps on the campaign map?

I was just wondering if it was possible to put custom maps created in the battle editor onto the campaign map. Because what i'm trying to do is create a flat map (all the campaign maps are too hilly) where the weather is changeable, so something like putting it on the campaign map and then using that location in the custom locations text file with sett_locked off so the weather is changeable.

If this isn't the case then is there any other ways of doing this such as making custom weather available for maps in data/world/maps/custom ?