ActionScript 3.0 :: Custom Class Inheritance And Property Accessibility

I'm having trouble accessing the variables of my main class from other class objects UNLESS the objects are extensions of the Sprite or MovieClip class, have been added to the display list as a child of the main class instance, and I am able to use the this.parent.variable syntax. What I'm wondering is, isn't it possible to have a simple Object declared and instantiated, residing in memory and able to access another object's properties, without it being a part of the display list? Am I doing something stupid here?

Let me explain the code a bit in case it's a design flaw on my part. (I'm still learning AS3 and am not completely fluent with it yet).

I have a project with about 15 custom classes. There are no frame scripts in the .fla file. I am using it basically as a library only. The document class (let's call it Calculator for this example) extends the Sprite class and specifies the properties for the SWF dynamically. All other classes are instantiated from this main class. I have a bunch of variables that I want accessible to the different classes, so to keep them in a central location, I have declared them in the Calculator class, and am trying to access them from the other object instances.

(It should be noted that there ARE animations that need to play at times, so I'm assuming I can't NOT extend the MovieClip or Sprite class when creating the document class.

For this example, let's say there's another class called XMLLoader.as, whos instance was created from within the Calculator class, that needs some information stored in the Calculator class' variables. Incredibly simplified code for the two classes might look like this:

Document class:

Code:
package {
import flash.display.*;
public class Calculator extends Sprite {

[Code].....

So, in the code above (I've bolded the most important lines in red), the only way I have been successful at accessing the variables declared in the document class from other classes is to extend the MovieClip or Sprite class when I create the custom class, add the object as a child of the document class (Calculator), create a generic variable cast to the datatype of the document class, and use it to access the variables.

This seems really excessive to me, and I'm wondering if it is, or if this is simply a limitation of ActionScript. Does, for instance, a URLLoader object actually need to be associated with a MovieClip included in the display list in order to access internal variables of the main class object? Is it me, or is that really convoluted? Shouldn't it be able to exist in memory separate of the display list and still have access to varibles declared from the main timeline (i.e. the document class in this case)? Is there no other syntax for accessing these elements? Have I done something limiting with how I've designed this or declared the variables?