Wizard button implementations should not be final

I dont know why the wizard buttons are final but this makes it hard to add custom behaviour to them. For example, we need to hide a button if it's not enabled. We had to re-create all buttons by ourselves to do that instead of just overriding the isVisible() method of a button.
Affects:
org/apache/wicket/extensions/wizard/CancelButton
org/apache/wicket/extensions/wizard/FinishButton
org/apache/wicket/extensions/wizard/LastButton
org/apache/wicket/extensions/wizard/NextButton
org/apache/wicket/extensions/wizard/PreviousButton

Suggestion: remove 'final' from class declaration