Updated info:
So the client appears to want the standard Serial # functionality (i.e., having the serial # auto-increment based on the last one used, prevent from using an invalid or already-used serial #, and allow for overriding the ""next"" serial # if for example they want to skip a range of numbers) however, they ideally want the serial # field to be optional.
But the other snag is that they'd like to be able to specify the serial # data during W/O Entry (similar to how you can now do that during S/O Entry). This is because they create certain work orders for work that outside vendors will perform, and they need to tell the vendor what serial #'s to assign to the manufactured product. Outside of just manually keeping track of the serial #'s they tell the vendor to use, via an Excel file or BOM/Item Memo's in MAS, is there a way to do this?