These artists wouldn't pull many sales by being on the poster, but they would definitely bring something special to the table:
Talk Talk (performing Spirit of Eden + Laughing Stock)
Out of all of those, Sunn might have had a chance last year after releasing Monoliths and Dimensions, and Snd might have a chance this year.
I think every year someone suggests Merzbow as a joke. I'm just saying: when the world ends during the Sunday headliner, 2012, Merzbow should be on the main stage.