Appears to be somewhat like WorldEdit in Minecraft. Couldn't be that hard, and would make many copy/paste things easier. How would it handle pasting? You say that they all will become 1x1s?
maybe some commands like
/replacebricks [a brick's uiname] - replaces all bricks in the selected area with a chosen brick, e.g /replacebricks 1x1f
/replaceair [a brick's uiname] - replaces all the non-brick parts in the selected area with a chosen brick, e.g /replaceair 2x3
/replace [a brick's uiname] - replaces everything in the area with a specific brick e.g /replace 4x4 Cube
/replacebricks could also have a second argument for replacing a specific brick with a specific brick, e.g /replacebricks 2x4f 1x1f
now this could get entirely confusing with using brick names as some will have spaces. I don't know much about torkscript but you could use the datablock name for the brick instead. and don't get me started on how confusing this would get with all the brick sizes. some math could be done, that tries to either fit as many bricks as they can in that area, or just keep filling until it is not allowed by the brick overlap rule. These are just some ideas.
