Yeah I understand what you are getting at, and I'm not sure there would be a way to fix a 3d printed can that had a baffle strike or some other type of internal failure. I dont think you can print on top of an existing portion of the can but im not really current on additive manufacturing so I could be wrong.
Its an interesting question that should be asked to one of the manufacturers that make 3d cans. No one plans on having a baffle strike but It would suck for a consumer if the only solution was a new serialized can with another stamp and form 4 process.