Would you want to have this done to keep spam away or is the community an issue (thus the need to moderate further?). In my case: guest cannot do anything but view the site, so, in order to actually use it, you have to be registered and ACTIVATED. Then I set the users to be able to leave moderation when they have a certain no. of points (not much, since I don't want to waste time with moderation). So any new user has 3-4 questions moderated (or replies) - based on my points system - and then, after I approve them, they can post normally.
Keeps spam away and the people who are clearly not there to spam, can use the community without being moderated. Would something like this work for you too?