Is it in LBB:2? So is it something a player can put on their ships? How much are they? Can you have a triple heavy laser turret?
Why would there be an entire design system in an article describing a single ship class?
If you want the design system, look in LBB5.
Is the design system for collector-based ships in JTAS#1? Can we use the Annic Nova without it?
No it doesn't. LBB: tells you how to build ships, this description lacks information on tonnage and cost.
LBB2 doesn't only tell you how to design ships, it also describes how to use ships; a physical model (how jump and thrust works), an economic model, and a combat system.
You can easily use the Gazelle as describes in JTAS in a LBB2-based campaign, move in space, transport people and stuff, and fight.
So where in TCS are the LBB:2 rules for special accumulators and heavy lasers?
Since TCS were after LBB5'80 there were no accumulators. The tankage described in TCS can be used with LBB2 and LBB5 equally, as e.g. done in TTB.
"Heavy lasers" have nothing to do with TCS, they are only mentioned in the Gazelle description, where it is also explained:
The barbettes, and their particle accelerator weapons are not specifically covered in Traveller Book 2. They are a variant drawn from the material in High Guard, and grafted onto Book 2. Specifically, the barbettes are 5 tons each. The particle accelerators should be treated as heavy lasers as in Traveller Book 2, subject to an advantageous DM of +2 to hit. Damage from such hits should be skewed toward crew casualties, and electronic and computer damage if there is no fibre optic back-up present.
And as a result inconsistent and often contradictory.
So, the discussion boils down to: CT isn't perfect.
Well, bohoo, no role playing game is perfect.
I would call CT very far from perfect, yet we are talking about it nearly 50 years later, so it must have done something right...
Just that we had design systems for worlds and ships at all was a revelation for an early role-playing game.