This may not be quite what you had in mind, but I find it to be very useful for many similar purposes:
CocoaGestures
I set my mouse's scroll-wheel-button to activate the mouse gestures, and you can specify gestures for any menu command. (And, of course, it comes with many default gestures for common commands.) While I use the right button's contextual menu for copying and pasting, I do use mouse gestures for delete/clear and for 'select all'. And the gesture-recognizer seems to be quite flexible.