Dear Ichida,
I don't think you have map this scenario in byd as technically this might not be possible. Reason being as follows
1. You create a SO for customer at company B =======> supplier as company A
2. This would create a PO(item type to stock) at company A with delivery to customer
This is possible and you can properly map invoice (customer + supplier) in this scenario in the scenario third-party intercompany.
However what you are asking for as follows.
1. You create a SO for customer at company B =======> supplier as company A
2. This would create a PO at company A with delivery to customer.
however you want the item type to be "Third party" in the PO so that you can get a new supplier into picture.
This am not sure whether can we map in the system properly with all invoice + delivery correctly.
From my understanding, you directly map your customer with supplier with a third-party purchase order.
Could you clarify the need to have the company A in this whole scenario ? What is your business use-case ?
Regards
Leo