Make /fill new sintaxes

I take this ideas from world edit, but i think it will be cool to add to the game, and will help the people that likes to build and makes things in creative (like me).

The first one works like this: the /fill will have a sintaxe, and this sintaxe will make the /fill make a wall of the block i want to. Like, it will have 4 walls, like a cube, but open in the middle.

The second one works like this: maybe there should exist a command that allows us to undo and redo things, like "/undo" and "/redo" from World Edit.

And this is it! I think that this things would make a difference in building.