Audio sync rather than only YouTube video
My idea is basically to do an Assimil styled approach but be able to incorporate your flashcards (or Anki) with it in this way: 1) listen to the recording, 2) transcribe and sync, 3) review with flashcards and, of course, be able to click on a word to hear it individually (which I think you have as a premium already).
So, if I could upload audio I could then use podcasts and other sources besides YT. I'd like to be able to import audio files (Mp3 would be the first choice) and sync them up just as your YT function already does.
Artur Zygmunt commented
maybe it would be possible to "read/play/download" from google drive?