I'd wonder why any live cd/dvd can't run??????? If one works then we'd assume any other similar distro ought to work.
You might be able to boot directly to an iso. Might check with www.pendrivelinux.com
for ideas on using grub4dos or even grub or grub2. Not all iso images can be booted directly. I'd assume mint can.
At the splash screen of kubuntu one might be able to select another location. Never tried it, someone may know for sure.
It gets rather complex but one could do a full or partial install of another OS within a current OS. Not really easy to do.
Fedora has a gpxe network boot I believe so a floppy could boot it.
You could create a gpxe boot cd or floppy to boot to almost any location.
Many people create a live usb. Tools exist on ubuntu to do that directly if you can boot to a usb flash drive or external usb drive.