I have multi Redo working, but I have to fix some bugs with it. It lags when you redo big builds, like the duplicator. I don't know if I should put a limit on it or not.
Hah! I could do it >:C
I have reduced the amount of lag by removing a feature from the MultiRedo. The regular redo still has the feature. It is a loop that for every brick created it loops through the entire RedoStack replacing the old Brick ID with the new Brick ID so you can repaint/whatever it with Redo. Taking it out of multi redo considerably reduces the lag.
When redoing Demo house (~140 Bricks) it would lag ~4 or 5 seconds. Now it does it instantly.
I'll release it later, once the Multi redo bugs are worked out, but I'm not going to put that functionality back in for latency's sake. I'll let you guys have fun with it, but if you want it put back in, I'll put it back in.