Runway: Set default route for all pages

I'm building a multi-lingual Runway site. The language is set like this:

<?php

$validLangs = array('en','zh','fr','es','pt');
$currentURI = explode('/', $_SERVER['REQUEST_URI']);
$lang = $currentURI[1];

// redirect to correct language if necessary
if (!in_array($lang, $validLangs)) {
  $browserLangs = explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']);
  foreach ($browserLangs as $thisLang) {
    $thisLangPrefix = substr($thisLang,0,2);
    if (in_array($thisLangPrefix, $validLangs)) {
      $currentURI[1] = $thisLangPrefix.'/'.$currentURI[1];
      break;
    }
    $currentURI[1] = 'en/'.$currentURI[1];
  }
  $currentURI = join('/', $currentURI);
  header('Location: https://'.$_SERVER['SERVER_NAME'].$currentURI);
}

// replace Perch title with current language title if it exists
if (!empty(perch_page_attribute($lang.'_page_title',['template'=>'title-nav-text.html'],true))) {
  perch_page_attributes_extend(array(
    'pageTitle' => perch_page_attribute($lang.'_page_title',['template'=>'title-nav-text.html'],true)
  ));
}

// set Perch lang variable
PerchSystem::set_var('lang', $lang);

I'm also giving editors the ability to create their own pages using a master template which looks like:

<?php
include($_SERVER['DOCUMENT_ROOT'].'/incl/set_lang.php');
perch_layout('global/header');
?>

        <div class="section">
        <?php
            perch_content_create('Content', array(
              'template' => 'shared/text_block.html',
              'multiple' => false,
              'edit-mode' => 'singlepage',
            )); 
            perch_content_custom('Content'); 
        ?>
        </div>

<?php
perch_layout('global/footer');

For this to work, every page needs a route that looks like [lang]/page-path. It would be great if I could somehow set this default route for all pages so that the editor doesn't need to create this route every time they create a new page. Can this be accomplished through .htaccess or some Runway setting somehow?