I'm sure you've lots of cool features planed but here's one you may not have considered.

I think you need ways of getting more quality content. To get this you’ll need to make it easier for uploaders to submit to your site. You could create a login.php page that cactches the username and redirects to a newtopic page that accepts the submit. This way people will be able to use autoposters on the site. Just name the fields the same as either vB or PHPBB or even both if you want. Only high quality uploaders you trust will be accepted by the login.php page.