Caetano,
currently what we do is
1. we have 2 boms for the header material, one with no components with prod version 0001 and other with real compoents with version 0002
2. mrp runs and selects 0001 with no compoents.
3. when we assign the orders to assembly, we select 0002 and now mrp knows dep requirements.
this is our approach now... do you see any issues? or do you know of any other better alternatives?