Well, lighty. Patty Duke played identical cousins (yes, cousins) in "The Patty Duke Show", though, of course, that
was intentional.
(Oh, boy, I'm dating myself again!!)
But I digress. I would soooooo like to see SB do this!! The quality of HBO productions is becoming well recognized (so much better than, say, the NBC "Crusoe") and Eddard would be a major role (not a cameo with a ridiculous wig) that would both suit and challenge SB and should up his exposure.