A few of the deckplan examples shown get closer to what I'm used to.

Some are a bit “cartoonish” but much better than blank rooms.
This comment goes beyond the initial intent of this thread, (but close), but I would like to see armor handled completely differently. If you have 5% or even 10% of your hull in anything, don’t you think it might show up on a plan? The problem is that it’s virtually impossible to show how “thick” the exterior “wall”/hull becomes on a deck plan. It all depends on the total surface area, shape, size etc.. of any given hull design. This is far to complicated for a rpg. But I have seen in past forums people calculating the thickness of the armor on typical ships, like a 200 ton far trader for instance. Normally you simply draw the ship, fill in the staterooms, engineering, cargo, etc… and ignore the armor, yet it still occupies 5% (or more) of the deck plan. If you look at the plan of a standard 200 ton far trader with and without armor, the plans don’t really change at all, yet where does the extra 5% go? Simply put, it is ignored for sake of simplicity. I know this is a minor issue but when tying to design options of ships with and without armor, it matters a lot. You lose 5% or more (and sometimes less) of your deck plan but it is never shown.
Sorry to sound like a broken record… but I would like to see armor treated the way GURPS Traveller handles it. Armor in GURPS does not add any appreciable tonnage (volume) but simply adds mass. The way GT describes it (The thickness of advance futuristic armor might be up to a meter thick in some cases, but for large capital ships, that thickness barely shows up as a heavier line on the deck plan.) So GURPS doesn’t remove available tonnage from a ship, but instead increases the total mass of the ship.
Unfortunately this system will never work with Mongoose or any other traditional traveller game mechanic. Because GURPS includes mass on everything, including the type/shape and composition of the hull. You basically add the mass of everything. All ship components have listed mass… staterooms, bridge, electronics, engines, everything… Then calculate how many tons of maneuver drives you need to reach the thrust you want. There are no cut and dry charts A through Z for drives. Higher tech level drives produce more thrust per mass than lower tech level drives. You simply divide your total ships mass by the rating of your TL drive, and you get the tons you need for a thrust 4 or 6, or 2 or what every you want. And yes, your thrust rating goes up and down depending on your cargo and even fuel load. So a ship empty of cargo and jump fuel will be much faster than when it is full of cargo and jump tanks topped off. When I ran GT back in the late 90’s I had 3 generic thrust ratings for each ship. Empty, average, and full. It is common for a free trader to have a thrust .5 for instance when completely full of cargo and jump fuel. It simply takes longer to reach orbit and a jump point when completely full.
In any case, Armor did not take away from internal space. The extra thickness of the armor on the hull simply does not reduce the total volume enough to me measure… at least in the GT RPG mechanic.
I know it’s a pipe dream but I would like to see something similar in mongoose.