Without changing the stats of any of the ships or weapons, here a just a few adjustments to the required license levels that I think would help balance them.

Plasma Cannon HK: This weapon preforms like a phased blaster on steroids... it's too powerful compared to its cousin plasma cannons and it breaks the mold of hard hitting plasma, rapid firing ions, and fast effecient phased. I recommend moving it to license level 2/2/0/0/0

Flechette and Flechette MkII: these can't really compete with the higher end weapons, but they would do well to fill the gap between the newbie weapons and the neutron blaster. I would recommend license level 2/3/0/0/0 and 2/4/0/0/0 respectively.

Basic Gatling Cannon: There really oughta be a level 0 large port energy weapon, and the basic gatling seems like the best candidate to me. It doesn't really see any action since it's currently pitted against the Gatling Turret. Let's make this one 0/0/0/0/0

Yellowjacket launcher: Seems like a good level 0 missile launcher.

Iceflare Launcher: same as above.

Stingray launcher: bump this up to 0/0/1/0/0, it's far more powerful than the yellowjacket laucnher, so it should have a higher license requirement.

Starflare launcher: I recommend 2/0/2/0/0

Charged cannon: with the 50 m/s speed increase, this weapon is too powerful for level 3 imho... what about moving it to 4/5/0/0/0?

Behemoth: Move this up to 0/0/0/9/5

Marauder: Move this down to 0/0/0/7/0

Orion Rev. C & IBG Cent need higher Combat license requirements.

Yes. Combat 2 is entirely too low for these, as the lowest-level Serco ship that can compete with them requires license level 4(!).
-:sigma.SB