I might just have missed something obviousnote this scratcher is being posted before the release of Echopraxia which may well answer the question, but why is it a case of Too Dumb to Live on humanity's part to recreate the vampires? See the ending of the book - and many reader's reactions - imply that the end result is some kind of conspiracy by the "resurrected" vampire race to take control of the Earth and blah blah blah... except the vampires weren't resurrected - they were recreated, out of existing Homo Sapiens stock. They don't have a culture, they don't have any memory of their time as the apex predator (because it wasn't "theirs"), and in the book as presented they aren't even given any reason to see themselves as a group as such, let alone motivation to act as one when they're also total sociopaths. So... why is this an issue?
Adding a bit to this, we only have the word of an Unreliable Narrator in-story for the true extent of the vampires' abilities anyway, since it later turns out that the godlike Jukka was not only not unaugmented, but quite the opposite.
Siri's perspective is confirmed in Echopraxia: even if Jukka was receiving help from the Captain, they're both already so far above human levels of cognition that we'd be unlikely to tell the difference one way or the other. He certainly isn't reliant on it.
Siri actually answered that question near the end of book when he ponders the possibility of a vampire uprising on Earth. Essentially it's not something as prosaic as taking back what was rightfully theirs, instead it's a question of what an ultra-rational predator would do on a world where its prey are willingly putting themselves to sleep.
Okay, as the note hints this one is answered in Echopraxia: in what is either a clarification or a retcon, the second book explicitly states that vampires are not integrated into human society, but rather kept restrained in cells and treated as test subjects and generally abused horrifically, with a select few getting wheeled out to answer questions on demand. While the first book potentially implied that vampires actually are corporate executives or researchers, the second clarifies that they are only owned by them at best, and treated as feral animals by the humans. Jukka is both uncharacteristically friendly (!), and has an extremely high level of freedom and responsibility (he's unusually privileged even having a last name). As it happens, very little of this ends up being important anyway.
It may actually be readers reacting to Siri's hyperbole. In one of the last paragraphs of Blindsight, right after Siri's understated "vampires are gonna kill us all" freakout, he immediately admits to being an Unreliable Narrator. And even before that, in his last conversation with Sarasti, Sarasti finally makes Siri understand that he, despite his claim of being only an uninvolved observer, is not exempt from seeing thing as he wants them to see and interpreting people's topology based on his own pre-conceived biases. Considering his wariness towards and fear of vampires which he shows throughout the book, and which are reinforced by Sarasti jumping him just to prove a point, Siri has an irrational fear of vampires. He also comes to the conclusion that vampires are the closest thing Earth has to offer to what they have found has to be the baseline alien in the universe — a being without self-awareness. They have also come to the conclusion that in the end, the baseline alien — for lack of a better way to put it — will inevitably overpower humans, who are not fit to compete with alien life. Additionally, Siri's father's message makes Siri think that something is about to happen on Earth, something vastly changing. Alone, hurtling through space, unable to communicate and bereft of his ability to see things from the outside, Siri's mind conjures up the doom and gloom scenario of the vampires taking over Earth, even though for a lot of reasons this makes little practical sense. Really, it may just be Siri's overactive imagination there, but since Siri is presented as such a competent narrator and not revealed as unreliable until the very end, we are encouraged to take his assumptions at face value.
Why don't the crew wake up the extra synthesist, military adviser and linguist towards the end? They learn very quickly that they need all the help they can get versus the aliens.
Their expertise was considered redundant with the active crew members they would replace. With the ability of the Theseus to manufacture drones and machinery for muscle and mundane tasks, there wasn't considered much benefit in adding more cooks to the kitchen. And even if the leadership changed their mind, Rorschach germinating nine days early robbed those crew members of any chance to recover from Cryo Sickness before the action.
