Getting an instance's main class

Say I have a variable that contains an instance of a class. Is there any way to return a “Class” object based on what type that variable is?

I wish there was something like this:

var button:SimpleButton = new SimpleButton();

function duplicate(target:Object):Object
        var mainClass:Class = target.baseClass; //Yes, I know the "baseClass" function doesn't exist. This is what I want.
        var cloneObj:Button = new MainClass();
        return cloneObj;

I am able to extract the class name in text format, and even all items that it extends and interfaces, yet I cannot find any way to create a class based on

I did find the function “getDefinitionByName()” and “getClassByAlias()”, but if I understand correctly, you have to first register those definitions.

Also, is it possible to extract usable Classes (not just display objects) out of externally loaded SWFs?