Is it absolutely insane to suggest the Genesis Device as the IC?
Three moments jump out at me. First, right after the urgent call from Carol about the Genesis Project, when Jim decides they have to go investigate. He tells Spock to command the ship. Spock demurs:
SPOCK: It was a mistake for you to accept promotion. Commanding a starship is your first, best destiny. Anything else is a waste of material.
And Kirk realizes he's right, and takes up his old post again--a significant step toward rejecting the idea that he's old and used up.
Then there's Jim and Carol, after he meets David:
KIRK: My son. My life that could've been and wasn't. What am I feeling? Old. Worn out.
C. MARCUS: Let me show you something that'll make you feel young as when the world was new.
(They go to see Genesis. Light literally dawns. Kirk's face fills up with wonder.)
And then at the end, when Spock's coffin lands on the Genesis planet (Seti Alpha 6? I couldn't quite get clear about that) with a flash of light:
KIRK: Captain's log, stardate 81-41.6. Starship Enterprise departing for Seti Alpha 5 to pick up the crew of the USS Reliant. All is well. And yet I can't help wondering about the friend I leave behind. There are always possibilities, Spock said. And if Genesis is indeed life from death, I must return to this place again.
MCCOY: He's really not dead as long as we remember him.
KIRK: It's a far, far better thing I do than I have ever done before. A far better resting place I go to than I have ever known.
C. MARCUS: Is that a poem?
KIRK: No. Something Spock was trying to tell me on my birthday.
MCCOY: You okay, Jim? How do you feel?
KIRK: Young. I feel young.
The three moments in which Kirk makes big turns (ultimately a Resolve of Change, I'd say) all involve revelations about the Genesis Project.
If it's not the Genesis Project, then I'd say it's Spock, because of the first and third moments above. But I feel like the moment with Carol and the Genesis Project is also an important one in the same journey. And the Genesis Project is itself a metaphor for rebirth....