You'll lose your mastering data. I personally wouldn't do it with an image, but if you do I would recommend talking to Fanuc. I would be concerned about a few things: because the options on each robot are purchased individually for that particular robot I would be worried about the legality of putting on an image that doesn't have the options paid for onto another robot, I would also worry about whether there will be hardware or firmware compatibility problems between the vintages.
If not an image, how do you recommend porting over points and programs in a controller replacement?