Raufbold I think that price is the major balancing point.
Sure, playing in sandbox gives you unlimited funds, but if you are designing ships for other modes (MP or BH), then you will need to impart some level of budget. This is the main challenge of building IMO, even in sandbox, as trying to design a ship with the highest effectiveness and lowest price is a good goal.
If you impart no budget limit, even vanilla can become "OP" as nothing prevents you from simply spamming as many parts as you please.
Worth noting that there are differences between the different fighter weapons. The better ones have more damage, but often different projectile speeds, shield vs. armor damage, cost, and power use per shot (basically ammo).