If you care about the security of these artifacts, why is their home directory (or their full disk) not encrypted? If they have access to the repository, they probably have artifacts downloaded on their laptops, so if the laptop is compromised, the artifacts are compromised anyway.
Edit:
Not saying temporary credentials are bad. But the reasons you gave seem a little suspect to me. A better reason is that you don't have to worry about invalidating the credentials when an employee stops working for you.