USENET 2.0 could be set up so only headers are transferred. Then third party groups could publish moderation whitelists that the USENET provider to subscribe to. If a moderated whitelist approves some content, then the server would download it via DHT so its locally available. If a user requests something in a header that hasn't been filled yet because it's not moderated by an approved whitelist, it would download it and then serve it to the user.

This would make it so content that's purely spam wouldn't be pulled to all the USENET servers. If a moderation provider started vouching for a lot of spam, it would quickly be removed by providers.