The only exception is how we handle Superchillers. I personally favour coming clean to the Sannin (and only the Sannin) that we have a rune-of-last-resort which we will deploy if and only if it becomes obvious we have lost the battle as a means of denying the Rift to the Akatsuki. While its area of effect will be contained within the Force Dome, it will not allow us to seize the Rift. We are under orders from the Hokage to discuss no further details and are indeed violating his orders in having discussed this much. (That the Hokage in question is Asuma and not Naruto is immaterial.)
Question: are the Sannin themselves going to be in the Force Dome bubble? Because if so, I'm leery of telling them even that much. 'If this goes badly we're going to kill you' is something we shouldn't even think particularly loudly around Orochimaru.
This seems familiar.
How about this?
"Are we agreed that the Akatsuki cannot, under any circumstances, be allowed to triumph? Very well. We have a single, final rune which we will deploy if and only if it becomes obvious that our efforts to prevent the Akatsuki from maintaining their possession of the Rift have failed. We are confident that it will kill any living thing which remains in the Force Dome. It will not allow us to win but it will ensure that they lose. We are forbidden from discussing any further details by the order of the Hokage and indeed are violating his orders by having disclosed this much."
It's honest. It heads off any other questions. And if we actually need to deploy it, then...the fallout doesn't really matter.
I don't know... The combination of "why don't you open with the winning move" and "why haven't you told me, your beloved uncle who cares more about survival than anything else" seems rife for a death-by-Orochimaru speedrun.
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With that said,
The new problems introduced by your repeated plan with more detail:
1. This plan requires Hazou to actively deceive the Sannin. We've
just seen that Hazou sucks at that.
We don't get to snark "it's
technically true that the hokage ordered it" when we know we are engaging in deception. If that is somehow insufficient, the paper-thin smoke screen of "... It will not allow us to seize the rift" is another attempt at active deception, because Hazou knows the answer to (and anyone in that conversation can immediately think to ask) "can't we just go in afterwards?" Even if the Sannin take a cognitive vacation, Hazou himself still knows. This plan just adds more and more deception. Are we agreed that we should minimize Hazou's need to roll Deception? If so, perhaps the disagreement lies elsewhere?
2. The consequences are not thought out. Let's go through with them. I will assume that Hazou succeeds in his unlikely deception for ease of analysis, as otherwise we've already failed massively anyway.
First case: The EM nuke is necessary, and is used. The Sannin now know, at least broadly, what it is. Orochimaru's To-do list has now been topped (along with, possibly, stealing the rift) by "why didn't my beloved nephew tell me about this when I specifically asked for such runes?", "the effect is eerily similar to a rather notable recent event", "I wonder if I can make this, and how that'd go".
In any of these cases, Orochimaru connects the dots. Through trial, reasoning, or memory he realizes or sufficiently closely approximates the specifications of the EM Nuke / Superchiller. Some of them can be rather immediate. Regardless, the outcome is the same:
Hazou is dead.
Second case: The rune is not necessary, and we luckily manage to destroy all evidence, somehow. It's great that Orochimaru didn't have to see it in action!
In that case, why tell them and expose yourself to case 1 in the first place? You can only lose.
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Finally the absurdity of "I have an ultimate weapon" <> "why not open with the winning move dearest nephew" is somewhat revealed by the thinness of the fig leaf placed gently over that concern in the repeated plan after the response to the previous.
I share your concerns regarding keeping Superchillers secret effectively in the current plan, and I think it should be executed very carefully with as minimal exposure as possible. As a demonstrative but not necessarily practical example, as minimal as "can we retroactively have a shadow clone start mining as early as possible".
I would sincerely welcome suggestions to minimize our exposure here! Can we brainstorm in that direction?
However, the suggestion that we preempt that failure scenario by telling The Last Man We Want To Know About Superchillers about Superchillers seems like a strategy that can only end in greater expected losses.
If you disagree that Orochimaru (the only other Runesmith as well as an Essie with an extreme combination of paranoia, severe self-induced (?!) psychopathy, and immortality monomania) learning about the capabilities of Superchillers is an overwhelmingly likely lose condition, that is a separate discussion. I assumed you didn't?
For your ease of consideration, here are my assumptions laid out as clearly as possible. Perhaps the error in them will be clearer this way:
1. The proposed plan contains more literal Deception than the current one. (Since Hazou gets rolled by the Sannin here, this is bad.)
2. It is imperative that Orochimaru does not learn about the Superchiller rune, or he will kill Hazou in short order. Ideally he'd never learn, but the relative simplicity of the rune (iirc), his intense focus on runecraft, and The Isan Event lead me to bekieve that this is a ticking timebomb. Thus it behooves us to gain maximal leverage, personal strength, and other support before that happens.