I think setting up a separate booting partition may be even safer, as GRUB and it's loading kernels etc can then live entirely in peace, and all kinds of distro changes can take places outside of the booting realm, the only changes to booting being kernel updates etc. I also wonder if installing GRUB from another distro might be a defensive move. Myself, I'm going to start using CentOS as a second installed OS version, to test out applications for Redhat Enterprise Linux (RHEL) use. So, maybe I will be installing GRUB from there, to a separate partition.