Either a separate dialog: --password-show
or a separate option --showpassword to be used with --password dialog
...which would provide a button to show/hide the password to be / being / has been entered.
I have been using the --password option to get password for wifi networks, which is often long gibberish.
Many wifi password-entry dialogs have a button so you can see if you typed correctly.
These days, when one is strongly advised to pick something long and complicated, more and more
being able to see the password (when it is safe, anyway...) is a good idea.