I don't know if this add-on exist or not. How it's going to work. Admin, Moderators and a new Usergroup can use the add-on if granted with permissions. When they create a topic. They will have the option to provide a screenshot of what the download is providing. A box provided to type the URL. So, when the thread is posted. It will let them know that it is hosted by a 3rd party and it's approved by a staff member or whatever the group members is offering.