Most importantly you'd want to start off with top notch members and the tech gimmicks would help you keep them.
I only know of one "modern" forum, http://vanillaforums.org/ where there are some add ons which let you do some of these things. Reddit source may also suit the task, but voting on "threads" would have to be de-emphasized and it's probably harder to add/remove voting, usage limits etc.. Same for HN source.
There is this debate forum http://www.volconvo.com/forums/ that covers political, religious topics. It's old vBulletin so it's nothing you haven't seen if you've seen internet arguments. Everything depends on the quality of members and moderators.
Not much you can do with that which hasn't been done since usenet.
As far as update streams, like twitter but with more characters, more activity than old school forum format, I'm not sure it would improve the debate. Quora's approach of sending updates about activity around your answers could increase activity without making a mess.