Aberration Spotlight rig

Made a simple rig for an spotlight with a chromatic aberration effect: http://www.blendswap.com/blends/view/74649

There’s some problems with it, and I am wondering if there’s a better way to rig this.

Here’s how it currently works:
A controll spotlight drives the properties of three child spots. A custom property called ‘aberration’ is used to controll how far the three spots are separated from each other. Each of the three child spots get an rgb color component from the controller. This results a chromatic aberration effect.

Duplication: It’s tedious to duplicate the spot because the objects that are not selectable or visible in viewport are not duplicated with it. Instancing the Group dosn’t expose the properties of the controlling spot. The fastest way to duplicate it is append the group from an external blend.
Updating: Changing the aberration property or the color works, but the changes are only visible in the viewport after a frame changed. Other properties like spot size etc only update in the viewport after saving and reloading the blend file. Fortunately everything works fine in the render, but the lack of viewport updates makes it much less convenient to use then it should be.

Is there any solutions to these problems? Or is there another way to rig something like this?