It sounds like you want to have a library of master visual files. I did something similar where I created AI template files for things that I needed to programmatically reference. It shouldn't be any more complicated than opening the file and making it the active document to work with and then referencing the named shape as a child of the active document. After you've harvested the attributes you want you could leave the file open for further references, or choose to programmatically close the file.
I would say though that depending on how frequently this script is run, and how many shapes you are thinking of have as visual masters, you might consider it to be more efficient to create one visual master document and continually reference it rather than have one file per visual master.
var visualMaster = File(app.path + TemplateFolder + TemplateName);
if (visualMaster!= null && visualMaster.exists) {
illustrator.open(visualMaster);
var myDoc = app.activeDocument; // Get a reference to the newly created document
// manipulate your object based on attributes in the opened visual master file
}
else {
alert(TemplateName + " not found.");
}