Business Development: Having multiple decks is important. We're trying to create a vehicle that will be suitable for many uses. Ferrying passengers, carrying cargo, whatever. You're the engineers, you figure out how to make it work, but the decks are a must in both cases. And I don't really care where you put the engine room, stick it in the top with all the control systems. I don't think anybody would have a problem with flying the ship from the engine room. I mean, wouldn't that be like super convenient?*
*This arrangement is far less convenient than conventional thinking might dictate, and not just for aesthetic reasons.
Design: For the record, the aesthetic appeal of an engine room is very different than a control center. We can put them on the same level, but I'm going to keep poking the agenda that they at least be separate rooms.
Engineering: Making the decking removable and configurable makes more sense than just insisting that there be decks. For carrying passengers having decks would obviously be preferable. But hauling cargo would be much better if we had a giant open space with gravity trackers. If we make the entire nose of the ship a set of doors, it should be simple to allow for the installation of decks on a separate production line after the main hull has been assembled.
Business Development: Nobody wants their ship-to-ship transfers through a pair of giant doors! You wouldn't be able to dock at any ports unless they were outfitted for a battlehulk! Beyond that, unloading passengers at a terminal would require a terminal port size that doesn't currently exist outside of your own ridiculous insecurities. We're also not going to eat the cost* of having to tool up three separate production lines to make two different configurations of one light frigate cargo ship, the margins aren't there for that kind of work, eh? Just make the decks permanent fixtures and put a normal sized door on the nose of the ship! Is that really so hard?
*Historically, Core Corp did have to eat a lot of the cost on the CarpWheel class. It wasn't profitable and was quickly disbanded.
Engineering: Fixed decks and a small hatch will make unloading cargo a lengthy and manual process. But we can pretty easily add a door off the back of the top deck that would be perfect for unloading passengers at stations and terminals on the ground, leaving the big doors in the nose for cargo configurations. Simple.
Design: Ah, sending passengers out through a hatch at the back of the engine room isn't a great user experience. I'd advocate for pretty much any other solution.
Business Development: See? That's a great reason. Another brain-blast! Manual labor is cheap in a galaxy with a population of hundreds of trillions. Fixed decks, door in the nose. Problem bloody solved.
Engineering: We can put the hatch above the engine room if we turn the engine room on its side.
Business Development: Are you #@$%&ing me right now?