I think that #1 is still enormously enhanced by the conference itself. You don't get the same experience if you just hang out in the area that week. (Or I assume you don't, I've not tried it.) The serendipitous socialization aspects are a big deal, even only looking at doing it with people who don't work at Apple.

I agree that #2 isn't all that important (although there are probably some people who learn better in that sort of environment) and #3 is basically just a free show that you get with your ticket and could easily be made completely separate.

I like the idea of a week that's just focused on direct contact with engineers, but I fear that it would end up in very inefficient uses of their time due to being flooded with people asking basics because they couldn't be bothered to watch the intro sessions. In general, I fear what would happen without enough structure. But perhaps it could be made to work, and it certainly seems worth considering.

The obvious first step seems like a bigger venue, though. Apple keeps saying they can't... but other companies pull it off, so I have to wonder why Apple can't.