Several items ...
 

1) Allow containers to be locked like other windows.

2) Add an option to lock the entire UI so that context menus don't appear when you click the wrong place on a window.

3) Fix that stupid fade bug in subwindows.

4) Make spell gems, hot keys, and the autoequip region into generic elements that can be placed in windows other than their default homes.

Not really an xml change, but ...
5) Add slash commands and hotkeys for dropping and auto-equipping items (/drop and /equip). We shouldn't need to use the mouse at all to perform these tasks.