Simple:
There are no weapons only for fighters, as the only thing that a fighter is defined by is it's engine and size. Adding weapons that are only allowed for a specific weight class would contradict the current design of the game and require extra dependencies.
It would also be completely illogical.
What? No, it's not that you couldn't put dumbfire missiles on a full-sized ship. It's just that there probably isn't much reason to, since larger ships don't need to keep their size down as badly.
Further good weapons for fighters seem to be small Railguns and reduced sized Lasers, and obviously Missiles which are best if your numbers are limited or the enemy has good close range weaponry, or if RP dictates that sacrifice even of smaller ships is unacceptable.
There has never been a lack of beam weapons for fighters. Even a Particle Beam, to stay outside enemy beam range, or with good enough engine theoretically a carronade, for a huge punch on point black range, would work.
But... even the smallest particle beam takes 5 HS, and if you want to actually take advantage of its constant damage, you'll need a decently sized fire control. I guess you could squeeze it into a 500 ton fighter, but how's a 500 ton fighter supposed to stay outside enemy beam range?
As for plasma carronades, the only advantage they have is that they're easier to research; they're otherwise strictly inferior to even a visible light laser of the same caliber - they've got the same range as infrared lasers, but they actually cost more! And a fighter isn't going to be mounting anything bigger than 15cm, anyway, so the research isn't much of a problem. (And, while they do more damage per shot than other beam weapons at the same tech level, they fire commensurately slower. I'm really not sure why anyone would use them for anything.)
But how does this actually tough the topic?
If a beam weapon on a fighter is good, why not allow for a better one that requires additional logistics?
As I stated before, Plasma Torpedoes weren't needed, but Steve used them to add flavor to the game.
So, does your recent discussion say something for or against Ammo-based beam weapons?
Because, currently, it is a tactical discussion; Sorry if I just don't see the point, but I just don't see the point.
The point is, if the existing options for beam weapons on fighters are all lousy, adding new ones is more important. If the existing options are perfectly workable, it would still be nice, but much lower priority.
out of1160, for a total of 70 points of damage to a enemy destroyer.... 
