Hi Aaron! Thanks for the response, and I kinda do have a suggestion.
Design map brush would be best.
http://www.worldpainter.net/ (worldpainter) is essentially a design level map generator made for the game Minecraft. Although much more dumbed down (doesn't have to generate most of the stuff L3DT does) it contains a lot of cool features that would benefit L3DT designer level. It has a flatten tool, for instance, that when clicked on a certain height level and dragged will gradually flatten everything to that level. It all comes down to being able to make the flatten area look like it translates well into the terrain without having that drawn out look.
If that made any kind of sense, let me know. haha. Looking forward to something!