I want LW to have a good shot at advancing humanity's understanding. For that it's not enough to be rational, you also have to be at the frontier of an area.

I disagree on two counts. For one, I doubt that LW is the best place to develop original research (i.e. to publish ideas and rough drafts and get feedback). For that, you want a different kind of forum or 'subscription list' or wiki or RSS feed. Something with fewer people, most of whom are likely to read what you write. Something more focused. And, more important than a subscription list, you also need a peer-reviewed journal, so that your finished research actually gets academically published. SIAI should create a journal. JFAI or IJFAI.

Second, I disagree that the only way to advance humanity's understanding is by doing original research. We can also advance mankind's intellectual heritage indirectly, by doing original pedagogy - by publicizing ideas and problems in an interesting way for a broader audience, and thus attracting more sharp people to working with you at the cutting edge.