My work about unatended Raspberrypi SQM unatended station is based in two principles:
1 - Mount a remote network based filesystem for store SQM data. 2 - A script periodically executed by cron service that ensures that the PySQM is running and the remote filesystem is mounted.
The implementation of these two points was done a long time ago using the Raspbian version of that time.
Now that version is obsolete and the current one (stretch) uses a new administration tool called "systemd". With this tool, it is possible implement both points 1 and 2 in a very easy, reliable and secure way... May be a day I will find time to do it...
But any way, my old solution is now obsolete and I do not recommend its use.
If, for study purposes you want to consult the old and now obsolete documentation, you can find it here.