This can easily be done with a text field and a custom dialog. You might even set it up with the Re-Login script step, but do you really need to?
You can also set up your buttons that access this layout to check account names or privilege set names and not change layouts for users with the wrong account or privilege set. The layout itself can be set to be inaccessible to users with the wrong privilege set and this can be a good "insurance policy" that if a user finds a way to that layout despite your efforts to prevent it, all that they see will be a grey screen with "No Access" displayed on it.
Phil, how would the text field work with the custom dialog to form a password?