I have tried to make the PKGBUILD of all core programs/utils/kernel module e.t.c for the eHD card. It is based on my Gentoo ebuilds, therefore the resulting structure (position of the files in the FS tree) is identical. As of Gentoo, you still have to install tftpd-hpa or dnsmasq or another tftpd manually and, of course, adjust the configuration files.
It builds for me, but I cannot test full functionality, so take it as
the pre-alpha release, therefore (for now) targeted for a desperate or an adventurist only. If you are Arch user, and brave enough, some testing would be nice

.