Do we know the Vengeance
would be the only one of her kind? For all we know, the class is in full-blown production already, with USS Dreadnought
undergoing clandestine trials for the third year, and USS Treading of Jeweled Thrones under Sandaled Feet
having her first major maintenance layover.
Kirk seems ignorant of the program, but he has been out in deep space already, and has been concentrating on getting back there for five years lately. The idea that the Dreadnought
program would be secret from the rest of Starfleet is sort of discredited by Marcus openly portraying that model on his desk, and by security on the dockyards not being particularly strict.
Possibly the only exceptional thing about the Vengeance
here was her mode of deployment: rather than being launched on a Starfleet mission with a Starfleet crew, she was confiscated by Marcus and a mercenary team for a private sortie, and Marcus fully intended to return her afterwards.