I also put my vote down for virtual machines (vmware or virtualbox). Also don't forget you can move your virtual machines all you want, to any computer. Having 5 different os-s on one computer sounds like a real headache to me.
From my experience most diag softwares run fine with each other...and the rest that is too complicated or too picky, like ford ids, xentry, bmw dis and sss can be run on a virtual machine. They may be a bit slower that way, but they'll last longer...especially if you make safety copies every now and then :P