In order to best use the space inside the ship, I would think that compartments near the hull would follow the shape of the hull instead of always being rectangular.

You're missing a mess and recreation area for the crew, unless that's a part of the area you've labeled "life support." I think it's a little peculiar that the only access to the ship's controls is through the life support area, again unless that's also the mess. "Bath" should probably be "head" if you want a nautical term. Or you could do something like the Traveller RPG, which uses the term "fresher" for a combination shower/sink/toilet unit.

Think about access to the ship. I don't see any sign of an airlock or a way to get cargo into the ship. At the moment, I am presuming something like a large cargo elevator—maybe the entire floor of the cargo bay drops for loading, or maybe there's an underside ramp, like the Millenium Falcon.

I wonder if a freighter would devote so much space to gunnery. Nixing the guns would give 50% more volume for cargo, which I imagine would be pretty significant on a small craft like this one. Of course, more cargo space doesn't matter if you get shot down on your way to deliver it, so that's going to depend on the environment in which the ship is employed.