I would like to repeat my suggestion that consideration be given to this much broader solution.
A much broader and costly and probably not simple solution would change the entire concept for outside processing from an item to a secial operation type that never gets time posted, just costs from the PO line. This could actually could also give some visibility to when otside processing was taking place and when it was complete according to completed operations, etc. Would be partcularly helpful for work orders lasting several days or more and even multiple outside processes. Again, probably a major task if this was perceived by everyone to be a better process. If this were considerd then the PO line reference would have to be Work Order Number and Operation number. $$$$$.
The concept that an outside process is in fact an operation step int the manufacturing process seems to make much more logical sense than some special type of inventory item. It really is just a labor step performed by an outside company. The purchase order is issued to confirm the cost and allow AP to process payment.
This, in my opinion, is one of things that while expensive, it will pay dividends in the long run to just do it right. Of course, I am lobbying that the "right" way is the special operation. Just my opinion and may not be shared by others.
I still believe that the ability to purchase actual items and receive directly to a Work Order is also needed. I just believe that the two things are different enough to have their own distinct processes.