This sounds really interesting but I'm having trouble fully grasping the idea. Are you able to post some code examples? That would be really helpful.
I have an extended Exception class that I can attach observers to. So in a live site I have a logger observer, error page presenter observer, and for some things even an 'adminAlerter' observer that sends me an email if some really bad stuff is going on. In a development environment I only use a debugger observer that displays as much information about the exception as it can.