I commend the prompt build, although a separate website might be needed for the networking features, an extension which puts a button on YouTube should be entry point or else people will just forget the existence of this service after trying it out once.
Of course on the mobile, the entry point cannot be a browser extension and anything YouTube related wouldn't be publishing in the official stores. I presume the best bet there would be to prove the success of web version first and later perhaps offer integration to 3rd party YouTube players such as NewPipe, YouTube Vanced etc; Although I doubt the ROI here.