I got a rough version of a Theme Manager application working for CAREO today. For now, it's a separate WebObjects application that uses UCRepositoryCore (and therefore CAREO.eomodel) to talk to the repository application database.
It gives an admin a way to list all themes, list components in a theme, and edit the componentXML (as well as save, transform, cache...).
I'll have it working almost 100% by Monday or Tuesday next week, and then work more on converting all components to the new componentXML format.
After that, I might look at making it a desktop application (Cocoa/EOF?). That would be a nice addition to the admin interface... Hmmm... User management too? Maybe...