Goody,
SHOULD? Are you advocating teaching the Sefardim Yiddish, so that YOU can be connected to them? There actually IS one language that has always united the Jewry – that is the same tongue in which Hashem Yisborach spoke to us at Har Sinai, in which Moshe Rabeinu wrote the Torah, and in which we say our daily tefilos.
Not having changed our language certainly doesn’t mean HAVING adopted midieval German, inserting few juicy Hebrew phrases therein. Interestingly, at the time Yiddish was spoken by the Ashkenazi Jewry, it was exactly the same tongue that the gentiles were using. Just because we never updated its vocabulary and syntax, it doesn’t mean that its origins had anything Jewish about them, not unlike taking on the dress of Polish nobility. At the time, it was a gentile dress, and only NOW it looks so, oy, freem.