The $configuration array of the AbstractController contains the values which are derived from TypoScript. However it is necessary to manipulate those values and add new values from inside of an extension.
Maybe a second $configuration array should be named $internalConfiguration. By this the original $configuration could remain available.
Or the $configuraion values should be changeable by a setter method.
At the moment you only have the init method where you can set the $configuration array from outside of the class.
The $configuration array of the AbstractController contains the values which are derived from TypoScript. However it is necessary to manipulate those values and add new values from inside of an extension. Maybe a second $configuration array should be named $internalConfiguration. By this the original $configuration could remain available. Or the $configuraion values should be changeable by a setter method. At the moment you only have the init method where you can set the $configuration array from outside of the class.