I know you jest, but it's not beyond the realm of possibility for some peer to peer system to exist, similar to bittorrent, which could distribute the load across viewers. Most people have half decent internet these days. This imaginary extension could recognise the YouTube video URL, check it's DHT to see if anyone else has it, and if not it could capture the YouTube video and redistribute it to the next person who looked up the same URL. Stale videos could be deleted after a time.