I think Eliezer believes that a team of soldiers trained by Jeffreysai would be able to precommit in this fashion and carry the mission through if selected. I think that, even if humans can't meet such a high standard by training and will alone, that there could exist some form of preparation or institution that could make it a workable strategy.

For example, I suspect Jeffreysai would have no trouble proposing that anyone designated for a suicide mission who reneged would be tortured for a year and then put to death.