I just thought this a few minutes ago, and there doesn't seem to be a plugin that can do this. I figured this could be a very revolutionary way of manipulating blocks with a clever usage of commands. I wish I could properly illustrate this with some images, but imagine being able to use this for repositioning a certain ammount of blocks that are classified to their own block types. This "outline is acting like a 3D scan of the object, and will have a colored outline pertaining to which block it is. This in return could result a much more efficient way of fine tuning a structure. Does this sound like something that is feesible? Also I think that there should be verticle slabs, and the ability to rotate blocks at will.