To be honest, I’m not sure I like all the ideas put forth. I don’t see a reason for a preview (and expect it to be quite difficult to accomplish) and even less for a search within the preferences.
We try to limit the configurations available and the panels that do exist should be obvious wrt what they contain.
It sounds OK to group certain panels for quicker access, like “Input”. But I think you’ll find that you’re either end up with many categories with few panels or few categories that have many panels that only tenuously fit in there.
I’d like to point that by clicking in the Deskbar on “Preferences”, all the panels are already listed in a window. It would be nice to show them also as big icons instead only in a list. But in a list, you have the possibility to use “type-ahead-filtering” to filter keywords. By adding a keywords attribute, we could make it easy to filter out e.g. “Input”, “Audio” or “Hardware”.
I imagined this GSoC task to be rather about how the existing panels could be combined and improved. E.g. Touchpad & Mouse, Keyboard & Keymap & Shortcuts, Screen & Backgrounds, Media & Sounds, Deskbar & Tracker, etc.
This panel condensation shouldn’t go overboard either. Some things are complex enough on their own. Instead it could be tried to make the GUI more consistent, more intuitive or just prettier.
I don’t want to sound too negative, however. 
GSoC is just starting and together with your mentors you can still steer your project in any direction.