Thanks for commenting on my AUR package firefox-developer-de, I always thought that it's rather silly having the many different language versions each be independently maintained with their own variations in the PKGBUILD.
The one thing I am missing from your PKGBUILD to feel comfortable handing over mine now is the lack of PGP signature checking when somebody builds the package. The way I did it is slightly hacky but it works and fails on a wrong signature https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=firefox-developer-de#n39 , are you planning on including something like that in your PKGBUILDs too?