Mesan assassin nanotech
I'm not going to go into very much detail about exactly what this is and how it works at this time. I'll simply make a few general observations, mostly about things I already planted in At All Costs.
First, this is something that works best for relatively simple "programming." It's not something which is going to work extraordinarily well (if at all -- and I ain't saying either way about whether or not it will) if it requires the use of the forebrain of its victim. I'm not saying whether or not it can extract information from its "vehicle's" memories. I am saying that it works best for what one might think of as brutally simple, very direct, purely physical commands/compulsions. Grosclaude was basically instructed or programmed to fly himself into the ground when he reached a certain point in his known, readily projectable flight profile. The actual physical actions required of him were relatively simple, and in many ways relied upon the same sort of autopilot "muscle memory" that a present-day driver uses threading his way through traffic while carrying on a conversation with a passenger.
Again, in the case of Timothy Meares' attempt to assassinate Honor, the actions he was required to perform didn't require analytical thought, didn't require complex manipulation of information and data. They required him to perform a relatively -- and please note that I use the word "relatively" -- direct and uncomplicated (which is not necessarily the same thing as "simple") physical action. It did not require the nanotech to acquire from him a complex security code, make him enter it into an armory gun locker, and then cause him to take out a weapon, load it, and conceal it about his person while stalking his target about the ship. It required the nanotech to recognize a specific situation in which Honor was vulnerable, then to seize a weapon, and open what was pretty close to uncontrolled fire in the confines of Honor's flag bridge. Don't forget the people that he cut down while he was swinging that captured pulser around to shoot Honor.
Now, another point. Please go back and look at the passage in which Bardasano is discussing the actual implementation of Rat Poison with Detweiler. She says that the vehicle they've chosen will require them to use a two-stage approach. The nanotech's part of the operation is to compel him to release the toxin as soon as his primary target -- Berry -- is close enough. The "second stage" to which Bardasano referred could be thought of more as a hypnotic compulsion. Bear in mind that this guy hasn't received the sort of anti-adjustment security protocols which go into military personnel. In other words, the problem that they face isn't that he would be inherently difficult to "adjust" but rather that traditional adjustment takes time even without the need to First break anti-adjustment protocols. Even assuming that there'd been plenty of time to set this operation up, they have to be aware that if there is a lengthy period of unaccounted for absence for their vehicle -- if he just "drops out of sight" long enough for a proper adjustment job -- then it's entirely possible that his family, his coworkers, his employers, the local cops, or someone is going to ask where he's been. Which, in turn, is likely to pop warning flags from any security types he then runs into -- like Harper S. Ferry and his friends.
So, what they did was to grab this basically innocent bystander, drug him, implant false, safely reassuring memories as to where his briefcase and the containers in it came from, then send him off to do his dirty work, depending on the nanotech to see to it that he carried out the operation (no need to worry about whether or not their "adjustment" would hold in the face of a suicidal action). He didn't trip any alarms in any of the people he ran into, including Genghis the treecat, because there wasn't any sense of alarm in him. He wasn't fighting a compulsion, the way that the assassin who was sent after Princess Adrienne was, because up until the instant that the nanotech activated, he wasn't doing anything except carrying a briefcase which he honestly believed contained nothing more lethal than a perfume atomizer.
Now, as far as the proposal which someone (and I name no names, Leon) came up with for using Honor and Mike Henke look-alikes to assassinate Elizabeth, I don't think it's going to work. I suppose that someone as determined to stick to his guns as you (please note the exquisite care with which I avoided the word "obstinate") might argue that if our hapless pharmaceutical exec can be handed this briefcase and convinced that he's always had it, then someone else could be convinced that they really were Honor or Mike. Unfortunately, I don't think it's going to be possible to do that with someone who would also be able to pass successfully through all of the security checkpoints between the outer world and Elizabeth. Remember what I said about the nanotech not really being interfaced with the higher intellectual functions. You can't use the nanotech to give someone information that they wouldn't have in the first place for them to make cognitive use of any more than you can use it to simply extract information from the brain of its victim. So even if you managed to convince someone that she was Honor, you couldn't provide her with the information she needed to be Honor convincingly.
Nor could you use "happy juice" to conceal the anxiety of someone being compelled to carry out actions against her will by the nanotech. By the time you got someone that "happy," they'd have trouble just standing up. For certain their fine motor coordination would be shot. And that degree of "happy" fog in the mind glow of Honor Alexander-Harrington or Michelle Henke would set off every warning circuit in a treecat like Ariel at least as quickly as the panic reaction when the nanotech kicked in. The Mount Royal Palace treecats all know how the mind glows of "Dances on Clouds" and "Soul of Steel's" cousin taste. The instant that they see someone who looks like one of them but their tastes totally differently from any taste the treecats have ever experienced from them before, then the alarms are going to go off and the imposture is going to be discovered.
All of which, of course, overlooks the minor matter of what you do with Nimitz and Samantha in the case of Honor. Honor isn't going to be turning up at any function without Nimitz. If Hamish is present, Samantha will be, too. And there is no way that you are going to come up with two fake treecats who can fool Palace Security and Ariel. Just as there is no way that you're going to be able to slip the same kind of happy juice to both of them, as well as their humans.
So while there is a certain delicious deviousness to the proposal, I think it's right up there with training seagulls to detect and dive on the periscopes of German U-boats during World War I. Sorry about that, Leon. ;-)