:) One tiny, though: "I don't think I'll do a clean install any other way again."
There's the wonder of Debootstrapping(followed by Chrooting). Though the only practical thing it's got going for it on an OS-less PC is that you can perform an installation whilst doing other things with the same computer (like listening to music, using LibreOffice, etc) from the Live CD/USB.
If you want to install a 2nd OS onto the computer you can use debootstrap from the OS on it and not need a flash drive, CD, etc.
Oh, and it doesn't need to involve a Virtual machine, just a directory (preferably an empty partition mounted to one since you probably want to be able to boot to it).
