As I read through this thread of Paul, I tried to extend the Importer without copying over the old importer code. It's pretty simple and straight forward. Below is the basic steps, I'm going to release a addon using this soon so you can see that later.
- Add your listener to load_class_model and extend XenForo_Model_Import
- Override the method named getImporter and wait for somebody calls XenForo_Importer_vBulletin, use the idea of XenForo_Application::resolveDynamicClass and you can extend that class
- In your class (MyAddon_Importer_vBulletin), override the method getSteps, catch the parent generated array and add your owns
- Add extra methods to your MyAddon_Importer_vBulletin to handle those extra steps (stepX, stepY, etc)