Frankly, I think they've reached the point of no return with Brody. I get that Brody, when he's not bogged down with drama, is a great character. And I get that Damien Lewis is a terrific actor. However, at this point, there's really no way for Brody to survive this mission and have his name cleared and go back to normal that wouldn't require the writers to take a one-way trip to Stupid Town. It just wouldn't make any sense...and the plot already doesn't make much sense (Brody somehow getting close to top officials in Iran's terrorist network despite the fact that both sides know he's a double agent at this point? Yeah, ok.).
Nicholas Brody IS a terrorist. Sure, he didn't commit last season's act of terror, But he is a still a terrorist and now the entire public knows it. There's no possible way to wash that away and have it make sense. The public would NEVER forget it. Top government officials not in on "the big secret" would never forget it. And no amount of Saul mumbling "we're playing the long game" is going to make it logical. It just doesn't work. And, even if the writers somehow figured out a way to do it, what next? Brody would be completely useless in the field as an officer of any high rank. The entire world knows him. He'd be useful as nothing more than a grunt.