Duplicating content isn’t a bad thing, only you won’t be penalised for it as such – it just won’t rank for anything, so it is worth writing your own articles and using articles from other authors to pad out your site a little to begin with. Basically make sure that the majority of your content is unique and your duplicated articles only account for a small fraction of the whole.
The author profile page is a great idea – you could use it to entice authors to publish more articles on your site on a regular basis.