I’d love to see a HN<->NNTP bridge. This would make it possible to use standard Usenet readers, which provide vastly superior functionality, from proper threading to scoring.
NNTP is one of the most under-rated internet protocols IMO. Solved a lot of problems that are worth solving, even in domains even further from its original purpose than this. Also, if I could use a news reader for HN I could take advantage of a local killfile. ;)