Most other WMS's offer a feature called "Aliases" where the WMS simply recognizes multiple SKU's as the same item. This is used to support things like UPC/GS1, retailer specific SKU's, vendor SKU's, etc...
There should just be another table in Infoplus called Alias with "id, SKU, Alias, Type, Vendor/Retailer, Notes"
1, ABCD, A-BCD, Alternate,,
2, ABCD, 23498724, UPC,
3, ABCD, H8K2-L, Vendor, Hong Long Clothing,
4, ABCD, 766352, Retailer, Bespoke Clothes Ltd,
Then Infoplus needs to refer to these SKU's whenever it's doing SKU operations, lookups, and filters. This solves a wide-range of problems including customer SKU changes, multi-sourcing, vendor labeling errors, reseller requirements, etc...
It should not need mentioning, but Aliases are SKU's like any other and must be guaranteed unique. The complication is that both Aliases and canonical SKU's need to be not just unique among their own set (table), but also when combined. A SKU used canonically cannot duplicate a SKU used as an Alias and vice versa.