Let me admit that I don't use Report Builder (and can't spell SaS). (You may want to stop reading...)
Instead, for similar requirements I publish a general use Excel workbook that imports external data from SQL Server views (or functions or stored procedures). On the server, I keep a user table where I can store, for an authorized user, their login id (Windows authentication) and report parameters like the organization code prefix which they are allowed to see. (The org codes we use include the hierarchy in the code; the more significant digits the smaller the scope. [I don't like the scheme, but it is what we inherited.])
The views typically pass the appropriate arguments from the User table to invoke a corresponding user defined table returning function.
The Excel query parameters specify refresh on open, and clear on save, so that a user without a valid user id and User table entry sees no data in the worksheet, and can refresh the Excel query only for the organization structure specified for them in the user table.