aif (and maybe arch-installer, depending on how long we will keep using it) should be compliant with the FHS.
See man hier or http://www.pathname.com/fhs/pub/fhs-2.3.html

the only downside is we won't start the installers anymore like /arch/setup or /arch/aif which may be considered "less cool". To me it's a sign of Arch maturing, though I will always remain nostalgic about the plenty of times I've typed '/arch' when installing a system.

the advantages are: standard compliance and cleaner makepkg/namcap output, we get to use the wonderful variable called $PATH (without needing to update it).