Opportunity Product Workflow/Business Rule

Working with a client that needs to take a stored value in a Product record (ProductID) and write it into the Opportunity Product in a custom field in order for us to do some SSRS reporting.  However, looking at the OOB relationships between Opportunity, Product and Opportunity Product, I'm not sure how to accomplish this without creating custom relationships and potentially removing some native functionality between the 3 entities.

Will this need to be done via JScript or Plugin? Or is there a way to accomplish this using the native workflow and/or business rule functionality?

Thanks in advance,

DC