maintenance.php file modification in proper way

Hi!
In case of any “WP Maintenance Mode” plugin update I would like to modify maintenance.php file in the proper way.

Is there any way to do it in custom plugin or in child theme?

The modification is simple:
echo “<h2>” . stripslashes($text) . “</h2>”;
->
echo “<div>” . stripslashes($text) . “</div>”;
thanks,
Grzegorz