In this update I added the following commands:

/setbiome <biome> - changes the selected area's biome to the biome specified in the first argument
/smooth <integer> - Smooths out the selected terrain argument 1 times
/hollow - Hollows out the selected area (turns the middle of it to air)
/move <number> [direction] - moves the selected area argument 1 blocks in the direction of argument 2
/outline <block> - Outlines the selected area with the block specified in argument 1
/naturalize - Changes the selected region to a more "natural" state by replacing certain blocks with different types and adding terrain features such as trees and lakes.
/removeabove <height> - removes all blocks above the selected area within its bounds
/removebelow <height> - removes all blocks below the selected area within its bounds
/snow [height] - tops the selected area with snow of the height specified in argument 1