Hi,
I am currently working on a OLinuxIno A20 limeX system which works in read only mode.
I use the code I developped here: https://github.com/lauhub/debian-to-readonly
I have small problems with armbian evolutions, since it uses, creates and modifies some files in some directories that should not be modified according to this page.
Example of files :
/etc/init.d/armhwinfo (modifies permissions of /etc/logrotate.d/armhwinfo)
/sbin/fake-hwclock (creates /etc/fake-hwclock.data