I believe most users call that "Ning"
Actually that's not true but many of the features you listed are already in Ning and there are quite some people who testify on leaving their traditional forums for Ning so Ning "lite" is a good base to start with, I think.
As for showing entire pages, AutoPager Firefox Extension
allows one to load the next presumed page when you reach the end of the forum. It doesn't always work and many forums don't support it but it gives you the convenience of an entire forum without loading it all to begin with. (Try it on a popular blog like Lifehacker to see how it works)
Other feature that I would want is optional check box for integrating Technorati and Find in Forums
results when doing a search.
...and finally this is probably more complication than it's worth it but it would be great if you can mimic Tangler's
real time forum chatting with forum posts so you can either directly get a preview of the forum contents without leaving chat or view chat posts on a forum post without going to the chatroom but it's not really beneficial, just something that might satisfy the twitter generation of forum users.
There's also some things that are more technological innovations than features. Cases in point:
-Being able to participate in a forum through rss, instant messaging and Adobe Air clients
...which would lead to:
-Being able to participate in forums using a mobile phone as conveniently as while being in front of the computer
...which would be helped by:
-Better voice to text software
-Better text to speech software
-An application which allows you to write several offline posts that can be sent instantly to several forums at a designated time and which would crawl all replies back to that application like a rss feed only for forums only. This would majorly increase all spam though so an alternative would be an in-built cocomment for forum posts.