if I change the campaign maps

[Mong0!]

... will I be able to play them over b.net?

[Sheliek]

Theoretically.

If you made or found a copy of the campaign maps (I assume you mean the Episode I-VI ones?), you could play it over Battle.net, yes.

The only point I could see in doing this is modifying the player into multiple sides, though this only would in my opinion only work well in a few missions. Having people to observe or help could work too.