I think there are two things going on here: 1) needing better documentation for installing X, and 2) desire to break off and start totally separate wiki for archlinuxarm.
None of that seems to me like it belongs in Development, but I am just an ordinary user.
I believe that most, if not all, of the software installation problems we have on our Pi's, are going to be basic to all of ArchLinux, and that if documentation in the standard Arch Wiki is inadequate, it makes more sense to improve that than to start another whole wiki. Raspberry Pi specific issues can get added to the ArchLinux page for Raspberry Pi which is already in existence.
The xorg driver section in the Raspberry Pi Arch Wiki page is minimal, it could be expanded to be more complete. I personally found no pages about installing xorg to be complete, though. Each installation has it's own unique requirements. I personally found the eLinux page for installing arch on the Pi to have the most helpful list of what to install, and posting in the forum when I needed help.