I actually like and agree with all of the ideas in the OP. The only one I don't really have an opinion on either way is the competitions.

The optional registration page is a great idea because I think not being forced to register, will actually influence more people to do so. I know that sounds weird but I think if it's not so in your face, they won't be so reluctant to. I try to do the PCP thing whenever I'm commenting on something but like Oli said, it would be hard to enforce.