Install/update package-wise from the live CD/DVD using the installed (unpacked) packages

Currently, most distributions have a "live CD/DVD" with a "preinstalled" system for demo/evaluation, and a separate "Install CD/DVD" with package files and a nifty selection tool for harddisk installation. Since both versions share about 99% the exact same files (just as "archives" in the installer case vs. "compressed file system" in the livecd case), this duplicates a lot of allocated space and work, and it should be possible instead to use the live version for real, package-wise installation without needing a separate installer CD or image. Knoppix is using a plugin for apt-get, which can install unpacked Debian packages from an already installed system, currently with a lot of quick&dirty workarounds, though. But, it's already possible to upgrade an installed Debian system, package-wise with dependency checks, from a Knoppix live CD or DVD, which is maybe a good proof-of-concept.