Allowing html tags for Administrators and Editors in WPMU

How secure do you think the code below is?

I’m trying to allow Administrators and Editors to be able to have these tags available when editing post content, but I wonder why they got removed from the list of default allowed tags anyways.

function tcg_wp_kses_allowed_html($tags, $context) {

   // Add required HTML TAGS for regular users 
   if($context == "post") {

      $tags['picture']           = array();
      $tags['picture']['class']  = true;

      $tags['source']            = array();
      $tags['source']["class"]  = true;
      $tags['source']["media"]  = true;
      $tags['source']["sizes"]  = true;
      $tags['source']["data-*"]  = true;

   }

   /** This filter is documented in wp-includes/kses.php */
   return $tags;

}

add_filter('wp_kses_allowed_html', 'tcg_wp_kses_allowed_html', 11, 2);