I have never used Arch. And it may not be worthwhile for OP. But I am pretty confident that I could get that thing working again.
Booting into a rescue live-boot distro on USB, mount the Arch root somewhere, bind-mounting /sys, /proc, and /dev from the host onto the Arch root, and then chrooting to a bash on the Arch root and you're basically in the child Arch environment and should be able to do package management, have DKMS work, etc.