The ability to have multiple virtual screens. That is, some kind of screen class that you make instances of. Then you can have your main screen, pop up dialogs on another without disturbing the screen below, etc.
Good idea, no?
Edit: and I'm going to add here request to be able to remove button listeners.. (and bubble up and down would be nice to, but one thing at a time here...) EDIT 3:

I just made this.

If anyone wants a class that can add and remove button listeners, compatible with waitforpressandrelease, pm me. Mine just probably isin't as fast.
Edit2: And I'm gonna add that you should be able to turn off that awful default beep that comes with button listeners. Besides, if I want to make my buttonlistener do nothing (seeing as they can't be removed...), it shouldn't beep!
