Yeah and just as easily you can put a try/catch around your code and do the same ajax logging.
Sure, that is possible if you want to spend the time wrapping every function in your code with a try/catch block. Most people don't, and so we provide automatic code instrumentation. You can't just wrap your js file in a single try/catch.
I understand why you'd rather not provide this as a standalone tool, but I'd much rather run such a tool as part of my existing compilation process than use your proxy service.