Don't. Just dump all reviews upon any product change (at least by default). Everything goes into a secondary bucket of "Old reviews for a previous version of th

Don't. Just dump all reviews upon any product change (at least by default). Everything goes into a secondary bucket of "Old reviews for a previous version of this product." With a clear notice that "product features or even core functions may be different". They love money and fees. They can offer a review process to keep reviews for a new version once manually reviewed and confirmed as substantially the same product, perhaps with new images of new packaging.