Appointment/Scheduling within ratings for BuddyPress/Drupal/Joomla

We have a client who needs a Wordpress plugin that will allow registered members within BuddyPress to schedule appointments with one another by the day/hour accompanied by some sort of approve/disapprove mechanism, reminders and ratings. It would work like this... A wants to chat with B on Tuesday from 10-11AM. A would post the request to B. B would approve/reject and notification would be sent to A. Reminder notices would be emailed to each. At completion of the one-hour chat each would supply a 5 star rating and short comment that would be added to their respective profiles. Client is open to using an alternate CMS, such as Joomla or Drupal, so long as there is some sort of profile/social solution for the members at the site - like BuddyPress. That said, client would prefer to stick with Wordpress and within BuddyPress, if possible. Alternate appstack for customization? Perhaps a bridge from WP/BuddyPress and some PHP and GPL scheduling solution? Ideas, thoughts recommendations? Thanks! Matt