Grub2 allows to boot from ISO. - make a friendly ISO way of booting for GRUB, that now it is'nt -
Then with a linux program for all the distros to migrate from them, including OSX and MS WOS ...
1.- Method 1 A) download and store the ISO - the dayly build - at any partition that exist that are not going to be formatted, or create one that will persist to store it.
B) detect grub2 if it exists and add the grub2 entry to boot from it calling "sabayon liveCD", - install the grub2 if it does not exist.
C) boot form grub2 with the ISo at the HDD.
2.- Method 2 from the ISO or from the DVD copy the ISO image to a virtual partition at RAM, the install from it with the grub method partition, for this method the Live DVD would have a minimal live linux distro plus an ISO image to copy, booting with a script that would make the RAM pvirtual disk, copy the ISO - inside the ISO or DVD - to the virtual disk, mount the ISO and install from it.
Any of this tow install methods would improve a lot the time of installation, at least in theory.
PS1: There are an App called Multisystem I asked to add to the repos, that I managed to compile, but without fatresize and xxd dependences that I was not able to compile from sources, but that does work well in deb and rpm distros, that allows to install from ISOs with Grub2 from a pendrive.
This app what does is to add entries to grub2 menu to boot the ISOs - there is not a standard boot system - and in cases as Sabayon extract archives "a la " unetbootbin, but keeping the ability to multiboot, what is the Sabayon case.
PS2.- the standard ISO slows the installation because after installing itself upgrades almost all the system, better if links at the main page are for the weekly or dayly build for saving this time. At least as an option.
PS3.- Done this, if it is done, Sabayon would be known as the faster installation method distro, and, of course other would copy this way of installing. The DVD is almost dead, and with USB3 in a near future, and fast "big" and cheap pendrives, it is time of adapt to this.
PS4.- Multisystem, if it is added to the repos, would be also added to the default programs, at least I find it very useful, much better than unetbootbin that already is at a lot.