[Hirn]

А это не подходит?

Object.oldRegisterClass = Object.registerClass;
Object.registeredSymbols = {};
ASSetPropFlags(Object, "registerClass", 0,7);
Object.registerClass = function(symbol, class) {
	this.registeredSymbols[symbol] = class.prototype;
	return this.oldRegisterClass(symbol, class);
};

Object.isSybolRegistered = function(symbol) {
	return this.registeredSymbols[symbol] != undefined;
};
ASSetPropFlags(Object, "registerClass,oldRegisterClass,registeredClasses,isSybolRegistered", 7);
ASSetPropFlags(Object, "registeredClasses", 1);