I don't see a Win Win being possible, as the cost of the manpower required to create a simple solution would have to be factored into the cost of the items being sold.  Part of the problem is that a large number of items are made for products that are (or were) at other stores, and many of those stores (or the artists who made those items for the other stores) are no longer at that location, have been updated to the point where the add-on no longer functions properly, have had their name and or PA's name changed, or were simply made for products that were once popular but have waned over time, or were never very popular in the first place.  Combine that with how many PA stores consist almost entirely of add-on texture sets for outfits and hair products makes for a lot of ground to cover and keep track of, especially when you consider that many of those stores are now being run by someone other than the PA who originally created those items.  Personally, I've always felt that ANYTHING that requires a specific different product to be usable should be automatically flagged in such a blatantly clear fashion that it can be seen without having to open the page in the catalog, as in typing the word ADDON in front of the name for every single applicable product, but instead every PA seems to have their own way of identifiing said items..