I didn't know whether it would even be possible; it appears that it is, but so difficult that I myself couldn't do it. For fun though, somebody managed to do it, so it's theoretically not impossible.

So what to do?
I've done it countless times since the migrations leading to systemd broke everything: you can just install Arch Linux following the wiki, install the packages and copy the configuration from the Overlay/home/arch folder in the sources to your user's home directory. A few adjustments are needed (commands to suspend/shutdown) but that's it.

CTKArch 0.8 will happen, though I'm not sure when due my lack of free time so far and the amount of work still required to do things properly. I've made some progress though, see the Dev section of the site.

pacman -R aufs2
rm /usr/bin/tzselect /usr/sbin/zdump /usr/sbin/zic
pacman -Sy
pacman -U "http://pkgbuild.com/~allan/glibc-2.16.0-1-$(uname -m).pkg.tar.xz"
pacman -Su
mv /etc/pacman.conf.pacnew /etc/pacman.conf
sed -i 's/^SyncFirst   = pacman$/SyncFirst   = pacman yaourt package-query/' /etc/pacman.conf
sed -i 's/^CheckSpace$/#CheckSpace\nILoveCandy/' /etc/pacman.conf
echo -e '[archlinuxfr]\nServer = http://repo.archlinux.fr/$arch' >> /etc/pacman.conf
rm -rf /etc/mtab /etc/profile.d/locale.sh /var/run /var/lock
pacman-key --init
pacman-key --populate archlinux #note: answer yes to sign the archlinux keys
pacman -Sf wicd filesystem
pacman -Rdd mach64-dri mga-dri r128-dri savage-dri sis-dri tdfx-dri unichrome-dri heimdal nouveau-firmware consolekit
rm /etc/fonts/conf.d/{20-unhint-small-vera.conf,20-fix-globaladvance.conf,29-replace-bitmap-fonts.conf,\
30-metric-aliases.conf,30-urw-aliases.conf,40-nonlatin.conf,45-latin.conf,49-sansserif.conf,\
50-user.conf,51-local.conf,60-latin.conf,65-fonts-persian.conf,65-nonlatin.conf,69-unifont.conf,\
80-delicious.conf,90-synthetic.conf}
pacman -Su --ignore glibc #note: say yes to replace the packages
pacman -Su
sed -i 's/#CheckSpace/CheckSpace/' /etc/pacman.conf
mkinitcpio -p linux

You can then reboot to repopulate /run and run the new kernel if you need to. (your running kernel’s modules aren’t there anymore)

Additionally, for the update to be perfectly well completed, I recommend reading the earlier news item about font rendering, as well as the one about the battery tray icon (last two lines).

The fix is simple: run rm /etc/profile.d/locale.sh as root, and pacman -Syu again.

Create the file ~/.fonts.conf as your user, with the following content:

<match target="font">
 <test name="family"><string>DejaVu Sans</string></test>
 <test name="style" compare="contains"><string>Condensed</string></test>
 <edit mode="assign" name="hintstyle"><const>hintnone</const></edit>
</match>

The name of the battery tray executable has changed, so you need to run as user:
sed -i 's/BatterySystemTray/ptbatterysystemtray/g' ~/.scripts/batterymon.sh ~/.config/openbox/autostart.sh