Well I played around some more with the example EA model that is included and noticed they had done something similar to what I wanted to do, but had to mess with it a bit to figure it out.
They create the PowerSubsystem IBD on its own at a lower level, then show it in the context of the pwr:PowerSubsystem within the Portable Audio Player IBD at the higher level. If you change the name of the connector in either diagram, it instantly changes in the other. Exactly what I need!....however, there is a catch.
This is done with the copy diagram functionality, and with that they only allow links for one element at a time on one diagram. So, if they had two PowerSubsystems, you run into a roadblock. You can copy the lower level diagram in with connections and all for only one PowerSubsystem using the shallow copy functionality. To do it for the second PowerSubsystem, you must use the deep or smart copy, which means you loose the linkage between the elements for instant updates with a given change.
So, you have to manage copying a new diagram each time with new properties, then copying the duplicate diagrams into the IBD you want all of them in (or write a script to do so?). Or, one alternative I found would be to copy the diagram, then use the feature where you can apply an image to any element. Then script that process. But, that doesn't allow any minor reorganization of the copied diagram.
Also, it would be important to note that there is no indication that I can find that two elements are linked or not between two IBDs. There really should be a more intuitive way to just add the connections and layout for a property in an IBD.

Full Size Image:
http://i.imgur.com/Q1tzrBB.png