If I were to tweak things, it'd be in the combat rules, not the design rules.
First is this:
The smallest ship puts out 250 Mw power; that's enough to power a small city. Warships vary from gigawatt to terawatt range. There must be tremendous heat output - I can't see how the heat exchangers wouldn't be glowing into the visible range. Even without that, a large mass within a light-second or two is not all that difficult to spot on infrared against the background of nothingness.
And yet, with 20 minutes to obtain a firing solution, your single laser has a 21 in 30 chance of missing when aimed at a nonevading destroyer-size target a light-second away, and a 10 in 36 chance of missing a battleship.
So, first thing, direct-fire beam weapons should be a lot more accurate.
Second: sandcasters. Against missiles, fine, but if my "unarmored" factor-40-by-Striker-and-MegaTraveller hull cannot withstand a laser shot, then that cloud of sand is going to be little more than a lightshow when the laser passes through it. There is no amount of ablative material that you can squeeze into in a sandcaster canister that is going to be noticed by a laser capable of penetrating over a meter of steel at extreme range.
Now, make a laser more accurate without giving the merchant some defense, and we've got a problem. We still need something to serve the sandcaster role. I can see maybe an "ink cloud" effect as a countermeasure - shooting cannisters of some high-tech goo that expands into a cloud of some EM-opaque substance octopus-style, briefly blocking your view of the target craft and interfering with targeting before it disperses. However, that premise would affect all weapons, and it would work both ways. Needs some thought.
Third: the damage table. Three issues there - invulnerable ships, the crew hit, and the fershluggin' fuel-tanks-shattered result. The crew-1 bit was resolved in errata, nothing to add to that: they followed the Megatrav bit of dividing the crew into sections instead of letting a crew hit kill 90% of the crew.
As for invulnerable ships: no. In combination with that +6 penalty to weapon batteries of factor 9 or below (anything but spinal weapons), the game allows for high tech ships, or planetoid-hull ships, to carry so much armor that they can't be hurt except by mesons (and a little bit by PA spinals). However, except for mesons, you can't shoot without exposing your own weapons to potential damage, and even mesons depend on targeting equipment that has to be exposed to work. So, a roll of 2 should always result in at least a weapon-1 effect, regardless of how much armor there is.
And, that fuel-tank-shattered result: what warship designer in his right mind arranges fuel tanks so they all can be taken out in a single hit? My thought was, modeling off the Fuel-N result, make it 10% of the fuel volume, minimum 1000 dT - the result still cripples smaller ships like destroyers, but battlewagons can absorb it. McPerth some months back proposed something like 50dT per weapon rating.
