if i could throw some ideas at you Some quick ideas if you haven’t already decided is to have a web config added after a firmware revert which does the following
looks at the disk size of the sd card and creates 3 partions last one ext4 500mb for /overlay second one ext4 500mb /root and first one fat32 for remaining disk space default or all three userdefined it then runs an extroot script to copy files from /overlay to /overlay and then set automounts and the ability to checkdisk on everyboot. (putting ext4 systems last so microsd is still useable in other non ext supported os’s
if user decides to revert firmware through gli gui it can ask to delete or backup up /overlay to overlay.001 then asks same for /root and then asks to wipe or leave fat32 then it disables auto mount and writes directly to /dev/mtdblock6 to factory default.
then reboots again to factory default from /dev/mtdblock6 . second reboot starts regualar reboot and then checks for sdcard structure and follows script to use existing and saved settings and create as necessary and create automounts again.
just an idea Iknow there’s mo more to it but just saying. should be doable since it is your hardware and not like the vast amounts of other hardware out there
some additional files might be needed. so network connectivity may need this as a setup after net access is achieved and this setup is done from the ui after initial setup