How about permitting downvotes to everyone after a submission has had a certain number of upvotes (say 10 or 20)? As you say, currently there's no way to say "

How about permitting downvotes to everyone after a submission has had a certain number of upvotes (say 10 or 20)? As you say, currently there's no way to say "there's nothing interesting on the front page" even if a majority think that.