@Kier: I'm a bit lost as for how to choose among the offered listeners. What would be a typical code event listener that would trigger your class in an add-on?
I'd like to display a thread with another template that I'd select from the URL, like this: http://example.com/index.php?threads/thread-1.1/&use-template=custom_template
Or I could also bootstrap XenForo with another parameter:
$fc = new XenForo_FrontController(new...