First Andrew, are you asking what would be a wish list of graphic representations on a deck plan, or the rules/game design mechanics used to design a Mongoose Traveller ship?
I’ll take a stab at both. This is coming from a registered Architect so I might want more than the normal gamer, simply because I'm used to seeing more detail and design elements on sets of plans… AND I pay very close attention to the living environment inside a ship/on a deck plan. I want to see how people interact with the spaces on board the ship, the living conditions, the actual REAL clutter once a ship is build out. If you think the spaces are cramped on a basic deck plan with a bunch of “empty” boxes of space, you should see them when they are filled with furniture, counters, equipment, pool tables, etc…. So if the question is actual graphics, I would like to see elements mentioned above as aposed to empty 2x3 boxes for state rooms and 2x4 boxes for med bays, 3x12 boxes or so for bridge etc… Again, its just me, but I think it helps players get a better feel for their “home in space”. I have enlarged drawings of my ship galleys for instance so the players know where the food processor, cold storage, cooking area, dish washers etc… are located. BUT if you are not careful the deck plan can become graphically too cluttered. Luckily I use Autocad and can turn on and off layers, print small scale plans on 8 1/2x11 without much detail, but then print out full sized plans on 24x36 for use with miniatures with all the furniture, toilet, equipment, etc… layers turned on.
If the question is what rule changes we would like to see in the actual game mechanics, I have a different take. First I completely agree with the iris valve being outmoded. Can it truly be airtight? Metal scraping against metal? How does it seal? And yes, I know it’s very high tech 2k years in the future so that could be the answer. I rarely use them in my designs, particularly since they require a large area around the opening for the individual blades to fold back into. I know it’s WAY too much realism since Traveller is after all a sci-fi RPG, but I mostly use hatches or sliding panels.
I hate to keep mentioning competing rule systems, since I DO really like 90%+ of the Mongoose game mechanic, but GURPS spaceship design has a lot to offer. GURPS completely handles the bridge different. It gives a range in bridge size, not 10/20/40 etc.. based on a ridged chart. GURPS bridges are designed around how many work stations you need/want. First you calculate minimum flight crew, and that’s how many spaces you need. Then you add work stations as you want. Each station takes 1 ton of space… that’s about the size of an average to large cubical in the typical modern office, 5’x10’, more than enough room for the seat, work/control surface, and clear circulation space to easily walk on the bridge. The average standard GURPS bridge is around 5 tons, but it can be just about any size you want. A GURPS bridge work station is also holographic and multi-tasking. It’s similar to a touch screen and can have any number of tasks at the same time, pilot, astrogation, gunnery, etc.. with an -1 for all tasks for each function on the control panels during the same combat round. Anyway, it’s a very flexible system. Other work stations, like gunnery, can be stationed around the ship, 1 ton each, but even those can be switched over to just about any kind of control you want. IMTU a DEDICATED control panel CANNOT be changed or multi-tasked, but you get a +1 to that task, like pilot or gunnery for instance.
Another thing I would add is air lock size. Currently I’m guessing it’s part of the “stateroom” generic public space.
Stairs. Since this was created in the mid-70’s I guess the thought at the time was that everyone would always use ladders and floor hatches. Also, pay attention to the location of your floor hatch. You realistically would not place a hole in the middle of your main passage. At the very least you would have a 1 box (5’x5’ or 1.5mx1.5m) space off to the side of the corridor for vertical circulation. But a fully enclosed stair, even if it’s a ship’s ladder, which is just a very steep stair, would be much more common especially on larger passenger ships. That and lifts as someone mention earlier.
For other ideas I would like to see life support equipment as a separate required space the same as GURPS has it. Landing gear taking up 2% or so of total tonnage would be an added requirement if I had my wish. This would be another advantage that non-streamlined “space only” ships would have over ships that can land… they get to keep more of their hulls volume for money making space like cargo or staterooms.
Sorry for the long email. There are more ideas but this is enough for now.