Category Defaults Premium Plugin

There is a really cool plugin called Category Defaults which enables the site admin to choose many default Categories for your wpmu install. However, it doesn't allow for subcategories. I thought this might be a cool plugin for WPMU Dev Premium to run with. I could see tying the plugin to Blog Types. For example, If Blog Type A, then run Type A Default Categories. The current plugin is located at http://natureofmind.org/30/default-categories-for-new-blogs/ and I copied the code here for easy viewing: http://docs.google.com/Doc?id=ah8hr3gk4rf9_51dhxsvrdj

What do you think?

BTW, does anyone know how to add subcategories just by looking at the code I have posted? Thanks
Terence