LR4 - altered RAW file - where is original RAW?
As you found "Rest" will undo edits. An alternate work flow would be to create a virtual copy of you image using Ctrl-' (single-quote) and edit (crop etc.) that and then export it. This leaves all of your edits on the original intact. And later, if you want, delete the virtual copy. You can have as many virtual copies of an image as you'd like.
A pixel is a terrible thing to waste.