General improvements to the UI. Not having one window close when I open a new one, not having to play musical windows when cleaning inventory or sorting through gear options, not needing to go in and out and in and out and in and- every time I want to switch between my retainer menus... Changing it so talking to certain NPCs or doing certain things doesn't stop me from moving things in my inventory or throwing them away, and so having a dungeon queue pop doesn't immediately stop me from being able to do anything else.
Unlikely, I know, but I can dream.