The pressurized, crew-accessible part of a WarShip is probably pretty small compared to the volume suggested by its outer appearance. We discussed WarShip layouts in another thread, and I maintain that you should imagine BT spaceships pretty much like submarines, as opposed to the vacuum-filled zeppelin airships you're magining.
Not to mention the difficulties of evacuating crew sections of the vessel to vacuum, then sealing them against pressure from outside when they were built for being pressurized from the inside.