Planning for Substitute components for ASCP Unconstraint plan?

****Unconstraint Planning***

1.     BOM has Primary component and Substitute component setup in ERP.

2.     ASCP created the planned order for primary component as demand came from Make Assembly.

3.     System has ZERO qty for primary component but it have enough quantity for substitute component and it is showing on planning workbench as On-hand Quantity. However, users cannot use substitute component because ASCP is not considering substitute supply for work order.

4.     Users wants to use the substitute component to make the final assembly.

Issue:

1.     ASCP showing plan order only for primary component and not consider the on-hand balance for substitute component.

2.     If oh-hand balance is not available for both Primary and Substitute and Material planner finds a cheaper price for substitute components then only option is to manually create the Purchase Req and Purchase order in ERP side for substitute item.