Custom virtual host config in WHM/cPanel

Today one our customer asked to separate error logs for the different virtual hosts on the server which controlled with WHM/cPanel. Default setup stores domain logs in /usr/local/apache/domlogs/ and one common error log in /usr/local/apache/logs/error_log. This makes customer unhappy because he wants to see logs by FTP.

Direct edit of apache config prohibited because cPanel will rewrite it after any change in virtual host admin panel. I google around and find useful doc which describes how to add custom part to any level of apache config.