Well, I was thinking of having it so when you hit a predetermined key, any bricks you recently destroyed would be put down again. It's like undo, except of getting rid of placed bricks, any bricks you hammer'd, undo'd, wand'd, or any thing else would be replaced.
Let's say I place down 4 purple 1x1's. I hammer 3 of the bricks, so I now have one. I hit the key three times, and viola, all three purple bricks are returned, so I have 4 again.
Yes? No?