I'm new to the whole concept of federation, so please let me know if I'm missing something fundamental, but with your proposal (subscribing to all c/pickles) works for when each instance has the same general rules for posts, but what about when one c/pickles on some server is actually about... dildos? (like r/trees was about pot, and r/marijuanaenthusiasts was about trees)?
Wouldn't your feed be polluted with pics and reviews of dildos when you want wholesome and healthy pickle recipes?
The supernatural