For companies that use the Packaging Unit of Measure to handle less SKU's, but that would want a UPC code per pack type, it would be nice to add a UPC field at the Pack UOM level.
A product may have the same UPC simply with different units of measure or packaging. The UPC really should be assigned at the unit of measure or packaging options for a product.
Alternatively it would help to remove the uniqueness requirement on the…