Very nice work, props!
Do you think it might be necessary/a good idea to keep a week-old backup (or at least a couple-day-old) of the database, in case GOG changes something again and auto-update borks stuff up?
At the moment I am keeping two backups of the database, 12 hours and 24 hours old. I'm considering extending this to 20 backups, i.e. last 10 days.
That said, I have never had occasion to use any backup, because when something gets messed up (and this happens a lot more often than you think) it usually affects only a small portion of the database and returning to an older database would lose us some new information (e.g. new games, sale price info). What I usually do is fix (temporarily or permanently) the affected area rather than revert to an old database.
For example, for some two weeks now (since a few days before the upgrayde), about 20 games on GOG have no Modes field data (e.g. Consortium). MaGog silently restores the old data of this field, so on MaGog the information has been kept complete throughout.
What is more useful is that I keep a running log of all the changes made to the database so it is always possible to see what an older value of a given field in a given game had been (and when it had changed).