Directors can't currently send anything in the way of group/user notification emails similar to OJS' "Notify Users" email feature for editors. I would suggest implementing the feature for Directors (not Track Directors) but allow them to specify contacting all/one of the following: 

[] Send this message to the users associated with this journal who have indicated that they wish to receive updates (x users)
[]Send this message to all users associated with this journal (x users)
[] Send this message to all readers
[] Send this message to all registrants
[] Send this message to all authors

Some of this functionality may already be present in the Conference Manager role, but it might be handy to allow a quick-access mailing-list kind of feature for Directors. 

Forum thread discussing this, for reference: http://pkp.sfu.ca/support/forum/viewtopic.php?f=13&t=3063