The EM would probably not be the place to do this since it manages the install, uninstall, update, etc. for extensions and does nothing in regards to an extension's XUL interaction with an app. Seems like this would need to be taken care of in the widget code when an accesskey, etc. is set for a widget.

This sounds almost like an unsolvable problem to me, not?
How would you imagine to circumvent keyboard shortcuts clashing with different extensions?

Yes!!

Actually what I think we need is a global keyboard shortcut manager for all Firefox commands, not just for extensions. Extensions would add commands to the list. Extensions would attempt to request a key binding but they wouldn't override previous bindings. Maybe when an extension gets installed if it requests a previously used binding the shortcut manager would pop-up and conflicts would be higlighted in red.

(From Alex: That's asking a bit much. :-) )

Sounds like a great usability improvement! Perhaps a do-it-yourself (shortcut-adding) system a la foobar2000 would be sufficent, although I guess something more sophisticated is required to make this an outstanding feature..

Completly agree with miguel: the global shortcut manager is needed, but since that is a bit too much maybe that aproach could be done just for extensions. The first requester should get the shortcut.

In addition to a shortcut manager, could you please add a manager manager?

(From Alex: I'm trying to figure out if you're serious or not...)