Undo would be nice, especially having one for mixing (i.e. fader, pan, EQ, and 3rd-party plug-in changes), but I would love to see a selective History instead. Much like what Photoshop has,
but where you can remove a change in the history without having to undo changes after that change. If it has a dependency, it will warn you, or be grayed out as un-undoable. I know there's a program out there that can do this, but don't recall what it was.