Not sure about your problem, but there are couple of issues about your approach of solving it.

The predefined directory for administrator's unit files is /etc/systemd/system/, /usr/lib/systemd/ is reserved for packages. And there goes only systemd "units", not scripts - systemd does not run scripts directly. You can put your script in /usr/local/bin or similar and reference it from systemd unit file.

If you are talking about SysV service script you can put it in /etc/init.d and systemd will happily manage it as its own.