Object.defineProperty in prototype

[Harbs]

In my question to minimize memory requirements in XML, I’d like to optimize the 
zero index accessor.

Right now, we have Object.defineProperty in the XML constructor. The byproduct 
of that is we have a function defined on every single instance of XML. Ideally 
that should be on the prototype object. This should drastically reduce the 
memory requirements for instantiating XML.

In JS, that’s pretty easy to do:

Object.defineProperty(thePrototype,"0",
        {
                "get": function(){return this},
                "set": function(){},
                enumerable: true,
                configurable: true
        }
);

I’m struggling with how to do it in AS3. How can we get a reference to the 
prototype outside the constructor or have the compiler construct this kind of 
function automatically?

Thoughts?
Harbs