Thanks steelgoose!
I tried to implement the missing pieces but I'm not getting everything right it seems. You can view my code here: https://gist.github.com/anonymous/ba9b41655310d677eeebcfe0b8aed11d
And an example output here: test.fzpz (21.3 KB)
Unfortunately, Fritzing crashes on my machine while opening this file. My guess is that my script generates a wrong zip-format for Fritzing to parse. Does someone know of an easy to automate way to generate the fzpz-files from the raw svg- and part-files?