Someone that knows what they are doing can pretty much fix anything. I think a lot of it is trial and error, developing techniques over years of various challenges. I'm amazed at what a true craftsman such as a Dewey Vicknair can accomplish, I know I don't have the patience or skill to attempt repairing a badly damaged stock but somehow these guys can do it and make it better than new.
Link is to what Dewey accomplished on my Fox, I never would have thought that stock could have been returned to usable not to mention good looking.
http://vicknairgunsmithing.blogspot.com/2015/12/restoration-of-fox-xe-grade.html