I built a search engine for lectures (https://www.findlectures.com https://www.findlectures.com), partly to explore this problem. I think what you're describing

I built a search engine for lectures (https://www.findlectures.com https://www.findlectures.com), partly to explore this problem. I think what you're describing would be challenging, but if you do work on this please feel free to contact me if you want to discuss ideas. My approach has been to obtain collections based on recommendations, filter out low quality material (bad audio, lots of ums, etc) and categorize it so you can explore freely. Someone has to fund free content, and the missing topics are a form of bias - I can't guarantee that there is a counter-argument to every lecture.