(repost)
Not sure this rename is good. I thing we're going to run in a name conflict here, because a WorldElement - as far as I understood - will be anything that's part of the world, including scripts, triggers, (internal)engines etc.
This builder (which actually is a factory or something as we found out^^) can only build these voxelbased things. Maybe another abstract class in this hierarchy is needed that is an "Object in a world" which consists of voxels and can be drawn or something.... what a worldobject used to be