I would have taken the Hornet design over the Ferret for a light fighter - the guns don't ever need ammo, it has some missiles for punch, is fast and maneuverable, and can get out of Dodge in a hurry.
Mass drivers don't use ammo and missiles miss.
We fight alongside Piranhas in Secret Ops on several occasions and they manage to be highly survivable in the face of the horde. That always impressed me.
If I remember one novel quote right, they reported that they were sending fighters out with half loads for the mass-drivers in End Run. We just don't run out during missions.

The Piranha... bites!
That's all semantics. In Wing Commander 2 you can tape the fire button down, come back in three weeks and your mass drivers will still be firing.
Mass drivers do not need ammo. Never are they simulated as needing ammo.
Was it in Freedom Flight where I read that mass driver rounds were the size of marbles?
I didn't find the Tachyon replacing the Stormfire in the Black Devastator to be of much use.