form, locate_template, template and permalink

I have a form
<form action="/index.php ?>" method="get">
I get /?name=joe&sn=doe&…

I can do

function page_template( $template ) {
	if ( isset($_GET['name']) ) {
		$new_template = locate_template( array( 'mytemplate.php' ) );
		if ( '' != $new_template ) {
			return $new_template ;
		}
	}

	return $template;
}
add_filter( 'template_include', 'page_template', 999 );

Before this it’s OK.

I can do an url rewriting with .htaccess to get
/name/joe/sn/doe but with rewriting it’s return a 404 page.