Comment 9 for bug 453087

I don't think we should be able to change the procurement type in the BoM. It may become unmanageable. (if you want to change a product, you must change all BoMs). The stock location has a good system to change the procurement type on the location (the location of a manufacturing order can be provided by the routing). This may achieve what you need.

So, if someone wants to develop such a system, I strongly suggest to do it in a separate module.