I think it would be powerful to include meeting and conference planning inside the Redmine CRM.
Plugin should provide the form of setting up the meeting subject, date-time, meeting-point. Meeting starter should have to select meeting members from the Redmine Users base.
After the meeting has been created, redmine engine should send email notifications to meeting members.

And the fine,
the meeting, attached to meet-members, should appear in the Redmine Calendar (like task), able to have the spent time attached to,
- and have the special information, like meeting journal, meeting final idea, been attached to the task.

The meeting task should have more than 1 "#issue_assigned_to_id" accounts, or custom field "Members", and appear in all members' AgileBoard.

This one will improve Redmine functionality in order and the Redmine Calendar.