Being willing to take on greater existential risks will definitely help in short- or medium-term competition, as your example shows (greater risk of famine in exchange for ability to conquer other societies). So no, I don’t think we can necessarily coordinate to avoid a “brittle” situation in which we are vulnerable to catastrophic failure. That doesn’t mean it’s not desirable.
Being willing to take on greater existential risks will definitely help in short- or medium-term competition, as your example shows (greater risk of famine in exchange for ability to conquer other societies). So no, I don’t think we can necessarily coordinate to avoid a “brittle” situation in which we are vulnerable to catastrophic failure. That doesn’t mean it’s not desirable.