A couple of other issues that don't really matter because Traveller has extremely loose rules for starships (it is an RPG of course, not a starship combat simulator):
1) Docking a spherical starship at a station is a huge waste of space, especially if you are docking externally. But with all ships (and objects) reduced to amorphous displacement tons, it really doesn't matter. In reality though you'd want longer ships so you could have multiples of them docking head in (or side, but whatever direction you do, it needs to minimize the dimensions to maximize the number of docking points).
2) Once you have anti-grav and you can build a ship that can take sustained maneuvers at high-G, the shape is more or less irrelevant in order to land on a planet. While a sphere is going to be slightly more aerodynamic than say a cube, either could land on a planet with anti-grav. If a ship can accept g-forces, it's structure should be sufficient to accept it's own weight in a gravity field. There are a couple of exceptions to that, especially when you get into distributed hulls, but for the most part the rule of thumb works.
3) If you were to mount a spinal gun, then your ships radius is at least minimally required to exceed the length of the barrel by some percentage number. You'd have to have sufficient space on both sides of the sphere to account for armor and other secondary systems that had to be close to the surface. If you look at the Tigress cross-sections, you see the length of the barrel runs most of the length of the ship. I'm thinking that artistically they added in the "armored aperture" to make it look like the ship had an eye. I don't see the need to have such a large armored door to cover the emitter. But it does look cool. And then on the 'rear' of the sphere they tacked on the engines, so it's not a true sphere. In the GURPS writeup for the Tigress it says "A large armored port protects the gun during non-combat operations; the port itself contains focusing equipment for the weapon beam." So at least the designers did a CYA for putting the port there in the first place.
4) Jump bubbles - ah, this is another conundrum. When MGT decided to get away from jump grids and go with the jump "bubble", all of a sudden it gets interesting. It's not explained anywhere, which is kind of sad because jump technology is the key to humanti's expansion, as it is with all other races. Second, just how in the hell does it work? Are there micro-emitters spaced evenly around the hull to spray out the charged hydrogen to build your jump bubble? Is the jump bubble created instantaneously? Cause if you were under power when you tried to jump you would be moving faster than the particles you ejected from the ship, thus part of your ship could be outside the bubble (gets back to how fast it gets built). Just stopping your thrust would fix the problem.
5) Another issue is maintenance. A sphere is possibly the worst configuration for when it comes to having to do heavy maintenance on anything placed in the core. Needle/wedge configurations offer (potentially) quicker access to a similar component.
But, since it's a game that doesn't address these issues (and others), the configuration really shouldn't be an issue. But it does give us something to talk about!
