Would be very practical to get the List on RightClick and direct the New Message Dialog on LeftClick on the TrayIcon.
I don't really think this would be a good idea, since the behavior wouldn't conform to how other applications use the notification area. Look at almost any gtk/gnome application, they all use left-click for show/hide, and right-click for context actions. I can't find any examples of an application that deviates from that.
And what would be in that context menu? An entry for "New Message".
You seem to be very unimaginative. Thats a great pity, but not my problem.
Saving Klicks would enhance Usability, I never thought about obstructive common standards or "design flaws" I'm sorry ;-)