This really isn't vital to the goals that you stated, but I definitely think it would be cool to have OKP email. It could draw more people to the site if executed properly.

Maybe a forum for musicians and artists to hang out not to discuss other artists, but what they are working on. This would allow people to pool ideas, collaborate, etc... and could very well lead to some sort of OkayCulture.
It would also give a much broader definition of "Okayplayer artist." Instead of claiming the 12 on the artists page, there would probably be a few thousand.
Maybe have a page like the front page dedicated to these artists, and have a weekly update showcasing music, poetry, visual art, etc.. that would be determined somehow to be exemplary, ideal, definitive, highly acclaimed, or just plain cool. A few contests here and there, maybe eventually even some kind of published mag or CD or something, which could get distributed to the hands of non Okayplayers. These boards would probably have to be heavily moderated to stay on the right footpath, but I think it would be pretty cool.

Some kind of organized directory of Okayplayers by region would be cool too. It would give an opportunity for people to meet eachother in person, and take the okayplayer idea far beyond these message boards.

Just brainstorming...

Edit: one more thing, I've seen other fansites create and post some sort of name tags that kids wear to the shows so they can meet their fellow board postin compatriates.