Hi Samuli, I think being able to have a customized front end portal such as this is a great idea, and really would help Moodle on the enterprise side.
My thoughts on this are a new 'class' type, where one could put things like dept. pages and faculty pages. But it will take some work to get something like this going.
In the meantime, you might look at the Postnuke portal, for which Moodle as been semi-modularized (pnMoodle). Postnuke (esp with its autotheme module and multisites option) would probably be the best way to accomplish a Moodle portal right now.
Long run, going the oppsite direction and integrating one of the excellent content development/management modules from postnuke (such as PagEd or Pagesetter) into Moodle as the core of a portlet course type might be a very interesting way to get portal features into Moodle.