Blanket Purchase Agreement - Controlling user access beyond Requisitioning BU

Summary

Other than BU, are there any additional methods to control user access?

Content

Blanket Purchase Agreement access is controlled by Requisitioning BU, I would like to know if other methods are available to further define the access of the agreement. For example, with Smartforms and Punchout Catalogs I am able to create and assign them a content zone to a specific user group.  I would like to apply the same control to some of our Blanket Purchase Agreements limiting access to a select number of users within a BU. Can you help?      

Version

We are currently using Fusion 20D, and will shortly upgrade to 21A