CASTING & RAW model management in WTPart structure

There's any body have an idea how to manage Merge reference model from the CAD document in the WTPart BOM structure?

It seems that out-of-the-box there is no way to have a member link between that merge model from the CAD document and the WTPart structure.

So basically here is my situation:

Within my company we create a lot of CASTING model which we create with the Merge Inheritance function in Creo Parametric. This to be able to have the base model with over stock and draft, what we call the RAW model from which we start to create the final model with machining feature. 

So basicall my issue is that I need to pobulated  that RAW model within my EBOM structure so the procurement team can order RAW and the MACHINE PART

Here is the default WTPART structure generated from the CAD structure

PS: Within that example the X-1 is a PART link with a CAD-DOCUMENT that have a merge inheritance!! At first I would appreciate to be able to see that Merge reference by default in the PART structure:

So basically to incorporate the RAW we just insert the raw under the X-1

Af first this seem to work but when the Procurement extract the (Component list report) from windchill the report ignore the MACHINE PART?

So the only alternative we have so far is to insert the RAW model at the same level as the MACHINE PART. But this mean that we have to insert the raw manually each time we use the MACHINING PART... 

Did any body have face that kind of issue and manage it a more efficient way?

My next step is to develop a component list REPORT with specific filter but this not seem to be easy!!

Thanks