You are making the situation far more complex than it needs to be. The issue is not whether the user should need the root password to make a system wide change. The answer to that is probably "yes".
The real issue is a user changing their time zone should require a system wide change. It only effects them. There are no security implications. Ergo no root password should be required. Ditto for adding a printer for the users exclusive use. Ditto for adding packages only visible to them.
The fact that these operations and others are currently implemented by making system wide changes (and thus require a root password) is the bug, not demanding the password.