This scripting work has also been around for years in CAD programs (which I use everyday) in the form of "xrefs." With CAD, you get a pop-up window letting you know when the particular file or version has had any changes saved to it, letting you know to update what is displayed, and if you were to open a file with references in it, they are automatically showing the updated version. Is this the kind of interface you guys were imagining?
Instead of placing a permanent full-sized previews, I'd like to have the option of using a simple linking file with information on size scale, and any other adjustments made in the non-aperture application. Perhaps you could even have the Aperture RAW engine re-rendering the file within this external application and offer simple Aperture control functions as a system-wide option for working with any external app. This would save the time and processing power of have the Aperture application open.
Dynamic updating, or at least this semi-dynmaic notification would be quiet useful, as would editting functions being enabled system-wide. At this point, however, it might just be simpler to enable a better publishing ability from the Aperture application itself.