Hi,
Please find below my observations.
Scenario A: Your soultion with MB1C - 561W is the perfect solution.
Scenario B: If its a customer consignment stock and still lying in your warehouse, you can load the stock with MB1C - 561 E (Sale order stock). Here you have to create the open consignment sale order in the system and the stock to be uploaded based on the sale order in MB1C.
Hope its helpful.
Regards,
AKPT