The current structure of cms: frames and clipboard UI metaphor doesn't lend itself well to a piecemeal restructuring process. You would need to overhaul the UI (a big job in itself), just to get started. A better approach would be to create a new CMS package and borrow heavily from the old one. In theory, the new one should be completely compatible with the old one, so at some point - once the functionality has been duplicated, the old one could be removed from the openacs distro.
