I did changed the default "admin" user name as you suggested to something else.
But now I want to change it again but it is not possible from within your plugin.
Please make it possible! :)
1. admin -> adc
2. abc -> more-complex-admin-user-name-85u2359246389234346
This is not possible right now within your plugin. If changed once the lights go green and it is not possible to change even a simpler username again.