How about this?

Author: highstrike

lib/Cake/Console/Templates/skel/View/Elements/Flash/default.ctp

@@ -0,0 +1 @@
+<div id="<?php echo $key; ?>Message" class="<?php echo !empty($params['class']) ? $params['class'] : 'message'; ?>"><?php echo $message; ?></div>

lib/Cake/Console/Templates/skel/View/Elements/empty

@@ -50,7 +50,7 @@ class AuthComponent extends Component {
  *
  * @var array
  */
-	public $components = array('Session', 'RequestHandler');
+	public $components = array('Session', 'Flash', 'RequestHandler');
 
 /**
  * An array of authentication objects to use for authenticating users. You can configure
@@ -840,7 +840,7 @@ public function flash($message) {
 		if ($message === false) {
 			return;
 		}
-		$this->Session->setFlash($message, $this->flash['element'], $this->flash['params'], $this->flash['key']);
+		$this->Flash->set($message, $this->flash);
 	}
 
 }

lib/Cake/Controller/Component/AuthComponent.php

@@ -0,0 +1 @@
+<div id="<?php echo $key; ?>Message" class="<?php echo !empty($params['class']) ? $params['class'] : 'message'; ?>"><?php echo $message; ?></div>

lib/Cake/View/Elements/Flash/default.ctp

@@ -85,15 +85,6 @@ public function render($key = 'flash', $options = array()) {
 		$flash = $options + $flash;
 		CakeSession::delete("Message.$key");
 
-		// backwards compatibility with Session->setFlash()
-		if ($flash['element'] === 'default') {
-			$class = 'message';
-			if (!empty($flash['params']['class'])) {
-				$class = $flash['params']['class'];
-			}
-			return '<div id="' . $key . 'Message" class="' . $class . '">' . $flash['message'] . '</div>';
-		}
-
 		return $this->_View->element($flash['element'], $flash);
 	}
 }