Thanks to diba, I got everything together again. I'm currently uploading a file containing all 4 german/english voices, so you can combine them whichever way you want.
The upload will still take a few minutes; I'll post the link once it's done. If you can't wait, here is the README already:
You can mix and match these files as you please. (1 male, 1 female, of course):
Samantha/Tom = en/en
Samantha/Yannick = en/de
Steffi/Yannick = de/de
Steffi/Tom = de/en (*) see below
Simply copy the folders into tts/data, overwriting existing files.
NOTE: If you start from a pristine configuration AND want to keep Tom as
an english speaker, you will also need to copy the files for tom again. This
is because the configuration initially present on the device reuses some files
from the female configuration. So the combination Steffi/ Tom, if not
overwriting Tom's files, will have Tom speaking a rather interesting
mixture of english and german.
Here are the tts-* files: http://ge.tt/9XeUvcC