I played around with the code and integrated the userregistration completely in the index.php (still on version 0.12.0, but i think it will work also with the new versions).
You can toggle the userregistration on or off via the line 'show_user_create_button' => true, in the default config.
When you are on the Login-Site, you can click the link above to get to the userregistration panel. I also implemented alerts which are shown at the same position as the other alerts.
The texts are only in german, but if you like i can create a english version for better understanding.
You can try it out here: Link
admin-user: test
admin-password: test
With a license key you as an admin can delete and edit the users normally via the admin-panel. In the test-link i removed the license key so you won't see my license key. 🙂
You can download the index.php file via this Link
I hope this will help you to implement a full version in an upcoming release. 😉