unionfs seems to work well with few problems
it occurred to me that it might work to mount /bin, /sbin, /lib and/or /mnt using unionfs ... so any changes would be automatically saved in, for example, /root/.bin or /root/.mnt
i haven't tried it yet, just thought i'd post while i thought of it
Unionfs and bin, sbin, lib
yes, why not ...
ya making the stuff from image.gz r/w may resolve some compatibility issues with scripts and things.