I really dont like the idea of having more or less rare components. Everybody should be able to access to the same parts for their ships for roughly the same money. Cause otherwise you would end up with a faction so large that it starts to terrorise the rest because it just has better equipment. I like conflict, but I don't like to be terrorised by some larger faction because there is a Pay2Win-esque type of system. Engineering and piloting skills should decide the fight, not who got the right parts
To balance the arc weapon you could make the arc weapon expensive to build by having it need rare components that are either very expensive to trade for or have it need materials that are a rare find when mining. To balance the tide-turning potential of the arc weapon make an armor set for fighter/ bombers that needs rare components that are either very expensive to trade for or have it need materials that are a rare find when mining. The armor set when equipped to the fighters/bombers makes them become invisible to the arcing beams targeting and they will only take damage from it if they are directly it by it.
Also about the arc-tracking weapon: The idea is interesting but I feel like we don't need to overdo on tracking weapons in this game. Let it have this WW2 feeling.