A squad-based instanced dungeoneering game, halfway between World of Warcraft dungeonering and Heroes of the Storm, but with community-contributed dungeons and dungeon progressions.

Specifically, I'd like people to be able to use something like the StarCraft map editor to design and build whole complexes and progressions of dungeons through which they and others can play (and potentially compete).

Ideally, the classes themselves could be customized/buildable.