BTW, you working on a giant file where all d-i translations are merged is a great thing.
I was just working on scripts for doing this for all languages in Debian-Installer. See script/l10n-utilities in d-i SVN tree.
I just tested the update-translations by using your Bokmal PO file as a reference and this worked like a charm. I even made Steve Langasek "angry" because I updated aboot-installer just after he uploaded it..:-) (no harm...we just joked about this...)
Some day, if you want to try my script, just download a full up-to-date SVN tree for debian-installer.
So long I have been using a script in d-i svn called gettext-helper. Petter has made this script. I have customized it for myself, but my scripting knowledge is poor, so I haven't committed my changes. I suppose your script will do the same as this script, so I plan on using your script in the future. But I haven't had time to look at it yet. Håvard