Kirk is Everyman with a "devil" (Spock) and an "angel" (McCoy) each giving him counsel. That's a wide open formula for writing any story.
I have to disagree. Kirk was never designed to be an "everyman." J.T. Kirk was always meant to be exceptional. He was the youngest man to captain a starship in Starfleet. He was an ideal - highly capable, highly intelligent, open-minded and prone to introspection while being robust and dashing. He questioned and was unafraid of the answers.
And I have no idea were one would get or justify the Spock as the "Devil on a shoulder" allusion.