Is it possible to add the elasticsearch server ip with a file configuration within config.php or another file ? That would be perfect for automatic deployment.
If you are doing automated deployment, I assume you would be doing something to set the unique options for the installation? So why not just piggyback that process?
1 line of code could do it:
PHP:
XenForo_Model::create('XenForo_Model_Option')->updateOption('elasticSearchServer', array('host' => 'elastic search IP here', 'port' => 9200));