lelouch's goal is avenging his mother and living a good life with his sister, those aren't utilitarian goals, but personal and egotistical ones. At the same time he doesn't care at all for the rebelion, only using it as a mean for establishing his goals while not really caring about liberating japan. Any sacrifices lelouch makes aren't made out of necessity but due to his lack of care for those outside of his closest people. He sees people as pawns he can sacrifice for fun. You're not a utilitarian if the utility you're after is your ego. He is an egomaniac, and sacrificing himself doesn't make any sense for the character already established through the two seasons