llTransferOwnership() with flag 0x4 still allows no-copy inventory duplication.
Call the function with flag 0x4, pending offer is created, disable Locked status, drop in no-copy object, accept pending offer, take no-copy object back to your inventory, repeat.
Similar to how the server removes no-transfer-for-owner content after owner change, it should probably remove no-copy-for-owner content in the original after this function (with flag 0x4) makes an offer.