I see catching an error, but I don't see how to trigger an error (unless you're not suggesting user errors?). Are you suggesting /ierror to trigger an error?
Either way, I see a few problems with this. Namely, using a separate event to catch an error means you lose you're original location. Where did the error come from? What was my state when the error occurred? How can I go back? Without getting access to pre-error state, or being able to continue from that state, this event is pretty much only useful for theming an error message and nothing more.
Do you know about the :error label functionality? Although it's not perfect, it solves most of the error related problems (it even supports, to a minor degree, "user errors"). The important part is that you keep your state, and you can gracefully resume from an error using this method.
