Question - Is the intent to leave this in for the core distro?  If so, would you mind adding the update queries to add the new records to the `#__update_sites` and `#__update_sites_extensions` tables?  You can use the [2.5.7.sql](https://github.com/joomla/joomla-cms/blob/master/administrator/components/com_admin/sql/updates/mysql/2.5.7.sql) update to see how we did it with adding the language install feature.