One more package that needs screen name is Lars Blogger.
What you can do, is when users log in to forums, you check if the screen name is empty. Then redirect to a page that says you need the screen name set up first before they can post. And of course create a hyperlink to update their screen name.
I think you can find a code snippet for this in lars-blogger package. Lars-blogger requires screen name in version 5.0.4, you might want to take a look there.
