Since Harvard took over, they have been releasing books similar to the Loeb Library series for the Middle Ages, but so far everything is in Latin, Greek or Old English, so no Chanson as of yet.

I got my Mommsen in hardcover from Germany - it is indeed unabridged, in two massive brick-like volumes. Whenever you're ready...well, I won't be. I am reading Norwich's History of Venice and Burckhardt's Die Kultur der Renaissance in Italien in addition to the Procopius, which is somewhat depressing to read.