My ideal society is largely libertarian, but it is wholly inadequate for solving this problem.

Libertarianism doesn't solve problems. It can still be set as an end goal, but libertarianism alone isn't going to get you there. It has some of the same problems of communism; not taking human nature into account. Libertarianism - and communism - would work, if everyone was of a libertarian or communist mindset. Considering they're not, trying to get there on those ideals alone is utopianist thinking.

We need someone with the balls to say "fuck the system, your power is meaningless". Someone who will do what is necessary, even if it is unpopular, or even immoral, to ensure that we do not die out.

Yup. My ideal scenario on that front, so as to still have some semblance of representationalism, is for someone to have the massive balls to run for election, campaigning as a dictator. Have your platform be that you're going to ignore the rules. That way you still have the will of the people as you bulldoze the system. But, that too is largely utopianist, although fun to think about. If we do get a dictator, I think it's unfortunately more likely it will be through violence. But you never know.