Not a bad idea. Greenpeace already has the option of having separate templates for different locales, and that's good.
One concern, though: I don't like the idea of using the original English (or Englisch, if you prefer) text as the key into the message catalog. It makes it too painful to change a typo if you then have to retranslate all the other texts.
Otherwise, the idea that you at least have the option of simply editing the .ADP file is nice.