SAP PP with by product

Hi SAP expert,

I want to consult about production with by product.

I have Material A as FG.

Material A have BOM item :

1. Material SFG with phantom assembly

2. Material Pack 1

3.Material Pack 2

In Material SFG's production , there is a "by product" which have good receipt using Tcode MIGO (MvT 531) . This "by product" will be used as raw material in next SFG production.

Based condition of by product, I will create 2 alternatives BoM of SFG :

1. without using "by product"

2. Using "by product" as bom item

Concern and question:

Because SFG is phantom assembly So there is no production order for output of SFG.

how can I choose alternative BoM of SFG in production order meanwhile PPIC only create production order for Material A (FG) only ?

I need help and suggestion for this case.

Thanks and regards

Anita