Regardless of how you define it, I don't think the Aventine would be the "flagship." It's more of an experimental ship, a test bed for new technologies. The "flagship" of the fleet might get the best, most advanced new toys, but not until after the Aventine has taken them for a test drive and made sure they won't blow up.
That answers my question. So we shouldn't expect the Enterprise
to be ordered to a shipyard anytime soon in the novel series to be refit with quantum slipstream drive?