The MARCItemFieldsToOrder syspref allows values for a set list of item/order fields to be sent in MARC file used in acquisitions. We should broaden that out to include any item field to support a broader array of workflows. Bug 24334 already suggested adding barcode, but I see no reason not to take that idea further.
*** Bug 41755 has been marked as a duplicate of this bug. ***
Agreed that it would be useful to have all item fields available in MarcItemFieldsToOrder. I have recently worked with libraries that need additional fields for item data they are getting from vendor. For example, they are using items.stocknumber, which is not mapped in the syspref.