addin users to search

Yes if you create a function and hook it to the instant_search_res filter hook, e.g:

add_filter('instant_search_res','user_by_meta_instant_search');
function user_by_meta_instant_search($res,$q){
	$user_query = new WP_User_Query(
		array(
			'meta_key'   => 'Your_META_KEY',
			'meta_value' => $q
		)
	);
	// User Loop
	if ( !empty( $user_query->results ) ) {
		$results = array();
		foreach ( $user_query->results as $user ) {
			$results[] = array(
				'title' => $user->display_name,
				'content'=> get_avatar( $user->ID, 64 ),
				'url' => get_author_posts_url( $user->ID)
			);
		}
		return $results;
	}
	return $res;
}