200.php

<?php

class HTTP_Exception_200 extends HTTP_Exception {

	protected $_status = 200;

	protected $_response;

	/**
	 * Set the response object to retur when requested from get_response
	 *
	 * @param Response $response A Response object
	 */
	public function set_response(Response $response = NULL)
	{
		$this->_response = $response;

		return $this;
	}

	/**
	 * Return the response
	 *
	 * @return Response
	 */
	public function get_response()
	{
		return $this->_response;
	}

}

usage.php

<?php

class Controller_Derp extends Controller {

	public function before()
	{
		$response = Request::factory('controller/action')->execute();

		throw HTTP_Exception::factory(200)->set_response($response);
	}

	public function after()
	{
		// Some super duper extra expensive code that I don't want to run or alter my response
	}

}