What would the advantages be of (theoretically, of course) having Drupal as an object-oriented content management system? So I answered myself:
I'm not saying that this will be easy to achieve. In fact, this will be incredibly hard to achieve, and would require an almost complete rewrite of Drupal. However, it is the way to go: hopefully we'll see some changes towards object-oriented programming as we move into Drupal 7 and Drupal 8.