Using YT videos on personal website, asking for trouble?

I am creating a site and want to download 100's of YT and other website videos and upload them on my site. Am I asking for trouble? These videos will not contain any products. A lot of these videos have links and watermarks from other websites. What's the best way to go about this?

ultimately, I would want to remove those watermarks and insert my own.

Could be risky, but what the hell...

don't see what's risky there... don't download them, use your custom player and host videos on youtube, why would you spend your bandiwdth when you can spend Google's one

They're giving you that option though their TOS doesn't allow using their videos on commercial sites but that's a joke and there are zillions of people using it so go for it