SD partner functions design in BW

Hi

have you already worked with partner functions in customer master data in SD ? how did you manage to design it in BW ?

here is the situation, currently in SAP ECC each customer have multiples sales representatives, and every sales representative visits the customer only for a specific product category, so for a specific product category and a specific client there is only one sales  representative.

Sales representative is designed as “partner function” in the customer master data (table KNVP)

The relation between a sales representative and product categories is 1:N and  evolves frequently

In the sales document, we have the customer and product, the product category  is a navigational attribute of product

the requirement is to display at SD billing document level, the sales representative linked currently to  the customer (not the one who was linked at billing time)

what's the best approach to design this scenario ?  a  hierarchy on 0cust_sales can solve the problem?

Thanks