Tricky Problem - Any Ideas? Taking Parts Out of Item in Stock

Does anybody have any ideas for this problem? The customer has a non-standard process. They are a distributor of construction and agricultural tools such as drills, saws, machines, etc. They also do warranty repairs for their customers.

Sometimes, they need to repair a tool or machine, but they do not have the necessary spare part in stock. In this case, they take a part out of a different tool and then use the spare part to make the repair (it entered in the Service Order Line as an item and cost of good sold for Service Order).

I figure that they could do a negative adjustment for the Tool and a positive adjustment for the spare part, but I always want to discourage the customer from adjusting their stock as it creates entries in a COGS account (inventory adjustment). Also, it will write off entire value and stock of the tool (which is not technically correct from a financial accounting standpoint).

Another method could be to create a new location and transfer the item to that location (for example, name the Location “Out of Service Tools”). Then they could do a positive adjustment for the Spare Part and then later do a negative adjustment for the spare part in future when the spare parts are actually restored into the “Out of Service Tool”.