XenForo 1.x ships with many built-in importers and they are present in every install of the software. However, this component of the software is never utilized for fresh installs and it is used only once for those who migrate from an exiting forum software, from there it just sits idle. That said, I think the importer component should be extracted out as an official free add-on. This will make the code footprint smaller for usual installs (hence fewer places of security issues). This will also allow independent updates to the importer. Those who want to import an existing board can install the add-on and once the import is over, they can uninstall it (if they wish so). I understand that a compelling reason to keep it in the core is to enable smooth bootstrap or out of the box experience, but people who use any forum software usually already know about add-ons and importers. Another alternate way would be to add a checkbox at the time of full download to add the importer component.