Well, let's think about fighters as a combat unit in general, and what possible advantages they may have over something larger.
The first problem is simply scaling the maneuvering system. That is more related to mass than anything else, but maneuver drives already scale. A 6G drive on a 100 dTon fighter is a drive that produces enough force to accelerate the ship by 6Gs. A 6G drive on a 10,000 dTon cruiser is the same thing -- a drive that produces enough force to accelerate the ship by 6Gs. Obviously the 10,000 dTon ships drive must be larger than the fighters drive, but the results are the same -- 6Gs.
That brings in to question the whole "agility" thing. Why can't a 10,000 dTon ship be as "agile" as a 100 dTon fighter? Assuming the ship is properly reinforced of course.
For example, in modern times, one of the advantages a air-to-air missile has over a jet fighter is simply that it can take more G forces and be operational. If a jet fighter can only make an 8G turn before either losing the pilot or simply breaking apart, while a missile can make a 10-12G turn, that means that the missile can turn at higher velocities or at a sharper radius than the plane. It's more agile.
But in space, we don't really have turns like planes do, as we don't have lift from the air. Planes use their wings to turn, not thrust. In space you can simply use your engines to turn. That makes a 6G fighter just as maneuverable as a 6G cruiser.
The only thing that can perhaps make a fighter more nimble than a cruiser is how easily the ship can turn itself around using auxilliary thrusters. It's easy to see how small thrusters on a small ship can make it change it's yaw/pitch/roll much more easily than a cruiser can.
But, at "space" engagment distances -- does that nimbleness really matter?
I can see that it might matter against a sublight impact weapon, specifically a missile. It's easy to see how a 10,000 dTon cruiser is easier to physically hit than a fighter. It doesn't matter how nimble the cruiser is if I'm aiming center of mass on it. There's simply more ship to "get out of the way".
I would argue that "nimbleness" relates to how fast one can turn, not necessarily accelerate.
With it low mass and momentum, a 6G fighter should be able to "out turn" a cruiser simply because it can change its vector faster.
For example, say in game terms using a Mayday style movement system, the fighter can place it's "next" marker anywhere within 6 hexes (i.e. 6Gs) of its plotted destination, whereas, the cruiser has a cone shaped area of change. Such that while the cruiser can certainly speed up by 6G's going forward, it's can't turn the ship off axis from its vector more than, say, 2 hexes. Or, more simply it can only change facing by 2 hex sides each turn (say), and then apply it's 6G vector from there, whereas the fighter can face any direction it wants.
This allows a faster turning ship, even with the same overall acceleration, to turn faster than a larger ship.
But with your generic Mayday system, where you can adjust your next marker by your G rating, a 6G fighter can not out turn a 6G cruiser.
So. Save for overall target size, what benefit does a fighter have then? Anything at all?
I think it's pretty clear that efficiency comes from the best ration of damage efficiency / survivability / cost (both material and staffing).
With speed of light weapons, maneuverability loses much of its charm. With cannons I need you in my sights for a sustained period. With a laser, if I can take a flash photo of you with a big X on your tail, I can send several megawatts of hurt your way as well. Then it becomes dependant on the cycle time of the weapon (i.e. how long does it take to fire a plasma gun from when the trigger is pulled and the gun fired). Simple image processing can tell when the target and the X overlap and the computer can fire the weapon.
So, simply put, I just question the overall efficacy of fighters at all in a battle. The only benefit to a fighter is perhaps overall survivability of the overall combat unit. It's hard to catastrophically take out the entire unit when you can only kill them one at a time. But when large ships are as fast as small ships, I think the draw to smaller sizes is lost in overall innefficiencies. The classic 4 Gun SDB may well overall be more efficient than 4 Fighters. Less crew perhaps, easier maintenance, etc. Ye Olde economics of war.
Of course this is where you get your min-max calculators out and come up with the 9990 dTon pocket cruisers.