Would love to see ideas that broke from the model of a single ranked list: let folks tune their personal penalty amounts and gravity; add random jitter to rankings and throw a couple random new stories onto each list; classify/cluster users by their votes, so people who vote for jokes or NSA articles or their neighbors' articles (automatically) see more of those things.
It's maybe a bit much to ask PG and co. to architect radical alternatives to HN, because HN is a handful as it is and, besides, I hear they have day jobs. It could be cool to let a thousand flowers bloom: publish most of the now-hidden ranking data (maybe not all, because it can be useful to obscure how anti-spam algorithms work); let users opt in to publishing anonymous votestreams for clustering, etc.; then let other folks use all of this to make their own homebrew HN frontends within certain limits.
I suppose that, too, is kind of a pipe dream, because opening HN up for people to easily build their own frontpages is far-from-trivial for both tech and policy reasons. But it's a nice pipe dream.