This was a fantastic article and lines up with some of the things I want to do on SN.
While I've been pretty vocal about having different types of subs and ranking algorithms, which should have some emergent design properties, I've also been wanting subs to be even more generic. Namely, the fields in a post form can be described by the creator of the sub; e.g. a before and after sub that allows 2 images to be uploaded, or a before, during, and after sub that allows 3 images, etc ... I think we could get communities emerging not just around content, but content types, and really surprise ourselves.