Because of the importance of good intelligence in administering a nation in a dangerous and often hostile world, is the occupation of spy a good candidate for a sacrificial mission life, where a soul goes in knowing that negative karma will almost certainly accrue, but does so anyway because the needs of the many outweigh the cost to the volunteer soul?

This, in fact, is done all the time. It is quite routine for the lightworker to take on the challenge of being human knowing that they will not be able to avoid such consequences when putting themselves into a society that believes in having a large standing army and other military apparatus, and perhaps even a draft system so they will almost surely be required to serve in the military as a youth. This is a sacrifice lightworkers make, knowing the odds they will get tarnished by karmic misdeeds of all kinds because they are growing up in a faulty culture and will not have the discernment they had as a light being, but more starting from scratch and will be heavily influenced by corrupted leadership, poor examples to follow, and a very low level of cultural sophistication in terms of ethics and morality. This is understood by Creator but the Law of Karma will nonetheless evaluate everything dispassionately, so these are "lives of sacrifice" by definition because they will incur not only risk to the soul and much suffering as a physical human but a karmic penalty in the bargain—that is a heavy price to pay for attempting to save and heal humanity, but it shows the goal must be highly beneficial and worth the cost or no one would do it. Keep in mind that everything is healable. Because all are soul-based beings, they are immortal, so even an act of murder is not a permanent demise but a temporary disruption in ongoing pursuits for the victim—that changes things quite a lot. That does not forgive the offense if such is the case in being a deliberate act, but it is a softening of the blow in terms of the meaning and consequences, so the karmic woundings accrued are more likely to be balanced out in a manageable way more than one might think.