Keeping with the YOLO spirit of the article, one can be even lazier, and do emergency R/O remount using this little thing:

https://www.kernel.org/doc/html/latest/admin-guide/sysrq.htm...

It's technically not an unmount, but still a pretty strong guarantee OS will not corrupt the image being written.

When done, reboot has to be done from the same sysrq handler, of course.