Are there any standard RPi images which mount the majority/entirety of the system read-only? Overlay schemes are standard on many platforms like routers.
Used to have a lot of trouble with my RPi getting corrupted (fixed with a new power supply). And rather than spend any time trying to make everything read-only in software I figured I'd just use the "lock" switch on the sd card. That was when I discovered that the lock didn't actually do anything.