Add an app to the dashboard that allows full analog stick calibration and control customization that all games would have to go through.
Change the music folder arrangements to be more like the original XBox where songs could be moved into different folders.
Add the ability to save playlists for songs on USB sticks.
Add support for user-made themes that control ALL aspects of the theme like Sony did with the PSP, they released a theme creator app for the PC, people used that to create their own themes that were far better than anything Sony ever made. Get rid of the stupid fog at the bottom of the screen and get rid of those fugly ass green boxes forever.
"Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety." Ben Franklin
Fully customizable control schemes. This is a problem for me when I bounce back and forth between certain games that have similar actions, but are on different buttons. Totally screws with my brain. I know, too, that some disabled gamers would like to see this as well.
Do you believe in God? Warning, your answer will determine how this game ends.