Make the downloading app/ interface a little like a file manager. Allow directories sub directories etc. Now enable users to save video to usb drive from phone or directly to any of the many cloud services. The reason to enable this kind of functionality is so that users can download the best videos while they are still up. Sadly they often get taken down so one cannot just add to favorites. Set up the interface so that one can easily download from your site to any cloud drive specified. Make the software compatible with theirs so that its seamless.