Replicating the setup when you need to reinstall? What?

I once had my computer crash during a kernel update and this left the system unbootable. All you have to do is use the arch iso and arch-chroot into your system to rerun/undo the kernel update or whatever other update broke your system. The thing is, even a "reinstall" is merely about deleting packages and then rerunning pacman and reinstalling your bootloader. Your /home and /etc stay untouched. You can take the list of installed packages and then install those. I mostly needed that when moving from an old laptop to a new one.