In terms of subscription/licensing, I believe "Business Stakeholder" only makes available access to very specific tasks, not full modules. For instance, they have access to Catalog Items...but not "full access". They can add comments and enter requests on behalf of others...but they cannot adjust the "assigned to" field of a Catalog Item, for instance. They can also view projects...but cannot edit them or add tasks to the, etc. When it comes to Asset Management, I do not believe "Business Stakeholder" has native/direct RW access to the CMDB tables (and by extension, Asset Management capabilities). You need "itil" (fulfiller) licenses/subscription, for that.
For more information see the following link. This is specific to CSM, but I believe would apply to the Now Platform, if you are only using ITSM Pro with Business Stakeholder - Business Stakeholder for Customer Service Management (servicenow.com).
Having said all of this, I suggest you speak with your subscription/licensing representative at ServiceNow as there may changes to the subscriptions/access, that I am not aware of...and/or they may have some alternate solutions, to fit your needs.
