Managing Custom Items/Part Numbers

Currently our organization maintains custom items outside of inventory with a non stock line type.  The business would like to create transparency around the process by tracking the components within inventory and hitting COGS.  There are two instances to consider: 1) the parent component is a purchased item 2) the purchased component is likely to be outsourced to have additional work performed on it.  Operations would like the part number to stay the same in both instances considering this requirement.  Is this best practice?  Any suggestions