I think that this is a must have feature:
Admin folder should be renamable without hacking.
This is now possible for wp-content why not for admin folder?
/** Wp-content Directory */
define('WP_CONTENT_DIR', ABSPATH . 'wp-content');
/** Wp-content URL */
define('WP_CONTENT_URL', 'http://localhost/wordpress/wp-content');
/** Wp-admin Directory */
define('WP_ADMIN_DIR', ABSPATH . 'wp-admin');