Red, I think your idea is brilliant, but I have to agree with Offshore regarding nixing the sand & the issues relating to the 60s materials/methods of manufacture vs those used today. The base material of vintage Rolex inserts just does not equate with what is used today, especially with cheap rep parts.
After trying various aging methods myself (including extended UV exposure within a salt bath using a UV lamp made for setting UV cement), I came to the conclusion that the only way to get a realistically aged Rolex insert is to get a Rolex insert that has naturally aged. Hands, dials & cases can be made to look old with enhanced patination, but I have yet to see a single Rolex insert that looks naturally aged by unnatural methods. That said, I will be following your work with great interest.