OSP process with PO for both labor charges and the additional components at Supplier side

Hello Team,

We already have a OSP process defined to create OSP PO automatically with an OSP item called Build_It. So when the PO is sent to the Supplier it will read Build_it = 1 pcs. The supplier does whatever he has to do and sends back the material. We receive it as Build_it = 1 pcs which actually completes the WIP job since thats the last operation.

Now we have a requirement to create a OSP PO which will include both the charges for doing additional work+the extra items supplier has added(This is going to different based on the Sales Model we are doing OSP with). So I want to know how I can create a PO with the Build_it+Paint+Varnish. So when I pay to the supplier I will pay for the activity Build_it and the newly added components Paint+Varnish I purchased from him.