The Debian-Live approach also provides some good opportunities. First and foremost, the very easy remastering makes it efficient to run with no persistent store quite often. For instance, upon remastering, I just start without the store, and the image I run is union-mounted with the persistence file and copied&compressed. Then I have to boot something else to copy the new squashfs image in place, but that's all that has to be done outside the system.

Boot the new image without persistence, create a new persistence file.
For further adaptations, the new persistence file can be mounted in an instance run under kvm, programs can be added and settings tweaked for an eventual new remastering.

Storing the series of squashfs-compressed images, one can always go back in this process if needed.