Hi,
many thanks for your report. It’s not 100% the answer you are looking for but maybe something similar. Probably you can use overlayroot. Seems to be an interesting alternative to keep your rootFS r/o and simulate a r/w file system for your applications due to overlay. I was playing with it and installation was quite easy.
https://github.com/chesty/overlayroot
login as user root
apt update
apt install git initramfs-tools
git clone https://github.com/chesty/overlayroot.git chesty
cd chesty
./install.sh
cd /root
nano .bashrc
ADD >> lines from GitHub
reboot
After reboot you can check mounted fs using mount command. It should show overlay mounted r/w as rootFS while the original root partition is mounted r/o to /overlay/lower
overlay on / type overlay (rw,relatime,lowerdir=/overlay/lower,upperdir=/overlay/upper,workdir=/overlay/work)
/dev/mmcblk0p2 on /overlay/lower type ext4 (ro,relatime)
In any case, do a full backup of your SD card before, to avoid any data loss or corruption.