One way to limit “Hull variant” module to 1, is to modifies the cost of your fighter to around -1000 (+ or - the cost of the fighter with a factor of the hull cost), and set their power production to -100.
On your modules, set there cost to 1000 (+ or - the cost of this module) and the power prod to 100 (or the power consume to -100).
Here you have a unique module without way to put 2 on the same hull.
More, you can limit who have access to this module by not modifie the current value.
(If you want an application of this, look at my Xedilco. The Wakizashi and the Buckler use this technique.)
I have look at your code:
[slots]
20.00,32.00,TURRET,
236.00,32.00,TURRET,
54.00,138.00,STANDARD,
202.00,138.00,STANDARD,
128.00,64.00,STANDARD
128.00,204.00,STANDARD
There are two thing who are missing.
First, coma at the end of the two last modules slot
Second, the 1= 00.00,00.00,TURRET
If you look at the code of the vanilla hull, you can see that all modules slot got a number. It is quite important.
The restriction to races is missing on the fighter Bomb.
Your scenario is very very easy cause it’s a lot of weapons spam. I suggest you to look at the “standard” ship of the game.
(To look at them quickly, copy the ship from “gratuitous space battles\data\ships” to “My Games\GratuitousSpaceBattles\ships”
You have much to learn, padawan, but you are on the good way.