Index: wp-includes/class-wp.php
===================================================================
--- wp-includes/class-wp.php	(revision 17488)
+++ wp-includes/class-wp.php	(working copy)
@@ -496,7 +496,7 @@
 	 */
 	function main($query_args = '') {
 		$this->init();
-		$this->parse_request($query_args);
+		do_action( 'wp_parse_request', $this, $query_args );
 		$this->send_headers();
 		$this->query_posts();
 		$this->handle_404();
Index: wp-settings.php
===================================================================
--- wp-settings.php	(revision 17488)
+++ wp-settings.php	(working copy)
@@ -69,6 +69,13 @@
 require( ABSPATH . WPINC . '/class-wp-error.php' );
 require( ABSPATH . WPINC . '/plugin.php' );
 
+// Add this as soon as add_action() is available to allow plugins
+// to add composible alternatives to front-end $wp->parse_request().
+add_action( 'wp_parse_request', 'wp_parse_request', 10, 2 );
+function wp_parse_request( $query, $query_args ) {
+	$query->parse_request( $query_args );
+}
+
 // Include the wpdb class and, if present, a db.php database drop-in.
 require_wp_db();