I think that the Debian dovecot package could be serving as perfect example; it 
creates a group, a user, has the respective prerequires on "useradd" and stuff 
like that, and it also installs config files. It has a -common package that 
mirrorbrain could also have (more obvious than "mirrorbrain" for the common 
files, and probably closer to the Debian packaging policies).

http://packages.debian.org/lenny/dovecot-common