To give it a bump (and such...)
I actually did this exact thing with Mint17 (I got bored...)
Manage to create a livecd (usb, what you want..)from my RUNNING install, with an installer build in to it, and customized to the bone.
The proces is rather easy and simpel if you think 'bout it, I'm 'bout to try it on my Sabayon install but before I can try it I need to make a decent full backup of my current Sabayon install.
Since I'm using Sabayon for about a week now, I'm still kind of in the "play and discover mode", but I really like the whole thing..
Like I said, its rather easy if you think about it..
The whole force (and it's magic) is the squashfs usage. So if you create a squashfs file of your running system, copy/overwrite this with the one on the original livecd...
Voila... You've reached your destination
Want the whole thing with an install option? No problemo, just install the installer (right...) right before you create the squashfs file...
This worked like a charm in Mint17 (and therefore in all Deb. based distro's I guess), but honest, at this point I've got no scooby 'bout how this goes for Sabayon...
Create the squashfs ain't that much of a fuss, copy/paste the following line in your terminal of choice, modify the settings in that line to your system and needs, and run as root.
Result is a nice clean squashfs file (a 12GB install, becomes about 2,9GB), copy/overwrite it to a copy of the original Sabayon livecd and try it..
mksquashfs /media/root/ /media/projX/Data/filesystem.squashfs -no-duplicates -e /mnt /home /dev
DO NOTE: replace /media/root/ with your SOURCE filesystem, and replace /media/projX... with the destination! Ideally this would be another hdd... LEAVE THE NO-DUPLICATES OPTION AS IS!! Last but not least -e /mnt /home etc indicates folders to exclude (hinch why -e..) You really want to add stuff like /proc, mountpoints. Otherwise your resulting file might get.. erm.. rather big hehe
Final thought comes to mind... Since Mint didn't care about kernel versions for this mather (vmlinux and initramfs used to boot livecd and the kernel inside the squashfs didn't need to be the same. My squashfs had the latest kernel installed, while the livecd was running behind. Result, running livecd uname -r gave the kernel version the livecd was running from, after completing the install uname -r gave the kernel version I had allready pre baked in Mint.
Again, this trick in Mint resulted in a installeble version of my customized install. So all the apps, software, settings, desktop theme's and even brwoser history was installed to the other system.
I used it as a backup tool... Fun to play arround, try stuff.. The whole things gets fucked?? Plugin usb drive reboot, hit install and within 10 minutes your back in the game, right where you were before messing things up.
Bit of a disclaimer... I'm not responsible for any data-loss or other losses (data, hardware or your mind) in case something goes wrong...