Could be one of the most radical changes in WordPress but it would save us over 1.2 MEGABYTES of space from wp-includes!
Though, it wouldn't be the same without TinyMCE, so it could be a core plugin like Akismet and it could be arranged to activate automatically on every WP installation. This wouldn't save us any space (since the "tinymce" folder would be moved from wp-includes/js to wp-content/plugins) but it could provide a much cleaner environment for plugins implementing CKeditor or other WYSIWYG editors.