Is it possible to create a read-only user account for security auditing purposes?
No, this is not plausible. It's technically possible to go through and create an account that has read-only privileges to everything, but that would be quite an undertaking, and there's nothing like that which currently exists, to my knowledge.
The issue is that, by default, most of the "configuration" settings you want to view are only accessible at all to administrative users, who can also modify them. So to create a read-only user that can access everything, you're basically looking at modifying everything (file system, registry, application permissions) to add read-only access for a given user.
Do like the rest of the world and have the auditors request information from the admins, if necessary, while the auditors watch the admins retrieve the required information.