Option 2 is
very unlikely. RFC hasn't spent this many books developing Thirsk's character only to kill him off so casually. Plus the text of the snippet says absolutely nothing about the bullet actually
hitting Thirsk, it merely states that the earl (which earl?) was hammered from his chair by the heavy bullet. The whole scene could be a dream for all we know.
I voted for option #1, part of an elaborate escape.
We know from as far back as OAR that Thirsk would have signed on with Tarot if it weren't for his family being held prisoner in Dohlar. He has an incredibly strong sense of duty, but he
knows he's fighting for a side whose motivations are immoral, and whose propaganda bears absolutely no resemblance to the truth. Despite the scene where he stands in fury while the Inquisition recounts the "kidnapping" of Princess Irys and her brother Daivyn, during which Thirsk counts the ways in which he's sworn to serve the cause of the CoGA, he
wants a better cause to serve, as Cayleb noted in OAR. Many of us have been expecting him to defect (or escape at least) if his family could be rescued from the Inquisition's "protective custody."
RFC has stepped in and cooled our ardor in this respect at least once, emphasizing Thirsk's dedication to duty, country, and the archangels. Thirsk's endeavors to improve the technology of his navy, their cannons, and their rifles shows that he's taking a lead role in helping the CoGA win the land war. He's managed to protect his tame wizard, and was instrumental in the creation of Dohlar's angle guns used as field artillery.
So for a guy who deeply resents the his superiors all the way up to the Grand Inquisitor, he's certainly acting like a faithful son of mother church. Of course we'd like to see him defect, if only to remove his creativity from the cause of the CoGA, and
he gives hints that he'd do it, except that his family is in "protective custody" to ensure his good behavior.
But if he were "dead," the Inquisition would let his family go, and I'm certain that Merlin could find a way to spirit them away. Of course that's what RFC
wants us to believe based on this snippet - for those of us who have learned to expect his sneakiness.
Since we can't believe option #2, an assassination, if we accept the obvious sneaky alternative, a setup for an elaborate escape, it's guaranteed that RFC has something even
more sneaky in mind. (Although I
still think Thirsk will join the good guys eventually.) As far as advancing the plot, I don't see how a staged assassination serves any purpose other than letting Thirsk escape with his family,
but RFC has shown his innate sneakiness in these partial "snippets" many times before, so we simply can't accept this scene at face value. The ellipsis make it clear that some of the scene is missing - perhaps a very
large part of the scene that would tell us what is actually going on. We aren't given the location, the context, or anything that explains
why Thirsk's faithful subordinate would abruptly decide to shoot him. (If that happened at all!)
Thirsk isn't killed here. He may be engineering his escape, but we simply don't know because RFC has deliberately withheld a crucial part of this scene. So as much as I'd like to believe this is part of a scheme for Thirsk to defect, and I voted that way, it's more likely that this scene is more sneaky than it appears. Those who voted for option #3 are probably going to be proven right.
This doesn't mean I've lost hope that Thirsk may eventually join the good guys, but this snippet probably obfuscates more than it clarifies. (Which is what RFC intended!)
Why does this entire post remind me of Viscini's drinking contest against the Man in Black in "The Princess Bride?"