I've got a working version of the theme management application running on commons, and it's coming along quite nicely!
Here's a peek at the Component List for a specified Theme. Note the indicators to show the status of each component. Green lights are good (i.e., the component has some xml to represent it, and it has been pre-transformed and cached.)
Selecting any component will take you directly to a Component Editing screen, where the xml can be edited (or copied/pasted from your Editor of Choice). Also, note the "Add Component' link: you can add new components from here, to fill out the theme as you go along.