since "sabayon" crashs i do not know what this tool offers
but why is this so complicated instead taking the physical
file of /home/xguest/ and copy them in the tmpfs-mount
before login?
needing firefox and some kiosk-app the prevent exit
firefox or start anything other on the machine and
some trick to restart firefox if it crashs
https://bugzilla.redhat.com/show_bug.cgi?id=720478