Ahab, as we've been playing him, is a selfless hero who fights so others can have a future. Willingly walking away and letting someone else sacrifice themselves in his stead so he can live is the exact opposite of that. It spits on everything we've done until now.
Staying is the IC option.
If the integrity of the character isn't enough for you, staying is also the option that leads to a CQC fight between two Big Bosses over who has the right to sacrifice themselves for the other. Who doesn't want to see that? That sounds fucking awesome!
Staying is the fucking awesome option.
I get that people don't want to lose Ahab. Really, I do. I want to keep playing as Ahab, too. But not at the cost of his integrity. And if that means taking a gamble that he's not the one walking away from this--and considering that his opposition is Big Fucking Boss, it's definitely a gamble, not a certainty--then that's just the way it is.