Role Security VS email workflows

Summary:

We have 103 Legal entities/Business units (for us Legal Entities = Business Unit), but due to legal requirements we had to create custom HR roles with AOR per business unit. HR & Executives can you view employee data for the plant they are responsible for. The security & AOR work fine but when we have an executive that needs to approve a transaction and they are not an employee of that Business unit they get a message "Warning:You dont have permission to access this information". We also have business unit roles for our managers and I've tried