Actually I can't think of anything you could do that blizzard would mind.
And even if you use a custom WE the license agreement still applys as It's Warcraft maps you create with it.
Actually, if you use no blizzard tools at any point, then they have no ownership over the product. In theory, if you could prove that no blizz tools were used, you could sell a campaign made without them legally.
Somewhere I found (and lost) a util that loaded & rendered war3 models. It was coded with C++ and DirectX. So I wondered if there was also something similar for the terrain...