Don't know if this
is what you after.
I use one rewriteable DVD, occupying only 2Gb, to boot 7 iso.
I think you are going to have a problem with put Ubuntu families into one DVD because they have directories of the same names.
The idea is quite straight forward. Just copy all the iso, after they have been expanded, into the master directory in a hard disk, substitue the isolinux with Grub, use Linux command mkisofs to turn the master directory into an iso, burn it into a DVD and that was it. I still use that DVD and may expand it further if I have time.
I extended the idea to do the same on a pen drive but only partially successful. The about link describes it too.