mattyp101 - Quad booting is an interesting concept and probably very restrictive on just how it is accomplished (having read through the two links that you posted). I do not have experience (yet) with Apple hardware but I have jacked around with OSX86 and multiboot setups. I found that boot loader and install sequence to be somewhat restrictive (one sequence works like a champ and a small variance will not).
The Apple BootCamp tool set works with an internal boot drive that has the hidden EFI partition and the main partition. The BootCamp assistant provides the partitioning for the BootCamp partition and takes care of the equivalent to a MBR, so the boot loading works. You then install a flavor of Windows or Linux and things just work (usually).
Doing anything else, requires that you find a boot loader that works for you. From my experience this is a learn by doing (or educated trial an error process, noting what appears to work and what doesn't). Very time consuming. rtEFI is interesting and maybe the boot loader that you need.
Anyway good luck with your project.
Neil
P.S. you know that your life would be a lot simpler if you would settle for virtual machines then you could run Vmware Fusion and have each of the OS's available at click of the mouse...