Having the ability for YouTube-DL to auto-update would be great, however, I'm aware of the security risks. What is the youtube-dl github got hijacked and malicious software was distributed? etc.
A solution to this would be to have the client compare the file against one on VRChat's own servers, then download if it is different.
This allows VRChat to update the youtube-dl file on the fly without having to push a whole new game update to Steam. :)