don't most clients work this way already?
With [Nostroid](https://chat.nostr.info/) I'm working on that solution. You only see what was authored by follows of follows of follows ... and what they comment on. It makes the experience of each user sort of invite-only but extended to 10k users or maybe even 1M users.
Discussion
I always saw PoW as something that you would need for public non-follow things like explore/public chats/etc.
You see likes and replies by non-follows usually. If they reply to you, you see it. In Nostroid that is limited to authors that are followed by follows of follows ...