1- chat would be nice...
2- file resumption from another server... altough I'm not sure that would be possible... and might invite more harm than good.
3- DO NOT add a freeloader filter. I don't like freeloaders either, but that also invites more freeloaders in a way... I could just as easily set my filter so high that noone could download from me as easily as I could share nothing.
Maybe this would work... give a filter option to block ip's sharing 0 files instead of a set number... that way everyone has to at least share one file.