I have Mail Monitor on my taskbar sitting next to several menus as I'm sure many others do.
When I am moving my mouse along that row of menu buttons it sometimes (for a split second) puzzels & annoys my that nothing happens when I hover over the Mail Monitor button. And then it just struck me, why shouldn't it behave like a menu!
The menu would have submenus for each of the filter folders Normal/Approved/Spam/Deleted, submenus for each account, and possably a submenu for unread mail. Each levels menu text would have the unread/total mails numbers as in top left pane of the standard interface. Opening the menus would open a submenu that looks like the right hand pane of the standard interface with columns for from/subject/size/date etc. although it would not be configurable directly the way that pane is, you could only interact with it as a menu. Clicking on a mail would open up the standard mail monitor with the dialog with that mail open in the message tab. Double clicking on the menus could also open up with that account/folder selected.