this can be solved by paid relays automatically whitelisting all of the follows of subscribers and clients publishing events to all of the user's follows relay list.

a lot of the issues you talk about can be solved with relays, clients even can be quite dumb. actually, the whole original idea of fiatjaf that relays should be dumb and clients smart, is upside down. the relays can be a lot smarter if you give them info to work with.