During past week, I worked on a new package called etcutils. It provides a (reduced) tool-set to programmatically manage files in /etc and is specially designed to allow pkgsrc to update /etc/shells and /etc/services in a more consistent way.
I'm happy to say that the 0.1 release is now ready! Go to the etcutils web page for details. (I know that if you are a Linux user, you probably don't care about this because your distribution most likely already provides something similar... albeit more complex.)
I'll now proceed to import this new package into pkgsrc as sysutils/etcutils. Later on (most likely not today), the following should happen: rework pkginstall to use the new shells(8) utility to update /etc/shells, add a new feature to pkgsrc to abstract the updates to /etc/services, and swipe through pkgsrc to make all packages touching this file use the new frameworky option. (Hey FAM, that includes you!)