There is one solution, have no free hosting, then it’s all magically gone. People who does this shit are only doing it because they think they can get away with it
Discussion
I think you are doing a heroic job, but you are also like Don Quixote fighting windmills. Please think about yourself first.
We either need a NIP to store encrypted blob fragments, which will remove any responsibility from you as a provider, or easy community content hosting. For example, right now only three people can post to shaving.kiwi, I know them all, and my only worry is that they sometimes upload humongous files :-)
Just because it is encrypted, it does not remove the liability. So, we either catch them and report them, or block them from uploading completely