[Arran]

I think it depends on how deteriorated the originals are, in most cases the finish could be "conserved" and touched up, much like they do with oil paintings and antique furniture. As for making replicas one might as well, so long as they are not represented as the real thing, which would be hard to do unless you have the original labeling, which would mean having an original hand painted set. Plus the effects of aging would be hard to duplicate such that it could not be detected.
Best Regards
Arran