The path I always use for updates is to install a virtual
machine, get everything the way I want it, then guestmount
the virtual image and rsync it to a hard disk partition where
I'll boot it.
Just need to fix any UUIDs and /dev/sdX that appear in
grub.cfg and fstab, then make a "configfile" entry in
your existing grub.cfg to point to the new one.
After you get the new one to boot, you can run
grub2-install and boot directly to the new partition.
(You also need to turn off selinux or force a relabel of
the whole new partition you just copied, I just leave
selinux off so I don't have to constantly fight it).
The great thing about this install technique is that I
never have to take my system down till I'm ready to
boot the new partition.