I think sacrifice is a good idea, but I'd rather see it shared as a perilous collective undertaking. A trial, or rite of passage, in which death, extreme deprivation, ingenuity and cooperation are components.
The survivors would then give separate reports on what transpired and how the others conducted themselves. On the basis of this information, the guardians will decide what positions the survivors will take within the establishment.
Guardians should be put to the test every 10 years, according to the position they hold and either promoted, retired or executed depending on their performance and the judgment of their peers.