Ok, having just looked at the OP, and followed a few comments, I see we are the RnD department, and all we care about is designing ships that appease customers.
Considering the backround of the system with the pirates, the need for successful trade, our local resources and our relative skills, I suggest our first build be sensor drones.
Cheaply made using outer ceramics that insulate the plastics within to ensure they do not melt and using simple propulsion methods to move around along with good ai and sensor equipment to alert ships with certain codes (merchant ones) of any unidentified ships. Since our dear coder has very hard to hack code himself, the pirates will struggle to pretend themselves as merchants. We also have silicon as one of the main exports on the planet, so making the sensors shouldn't be an issue of cost.
It's simple, cheap and merchants will be interested in buying and deploying them for their own trade routes. If it was possible, I'd love simple cloaking, but the emphasis is on a cheap early-alert system.
We can work on a combat ship/drone afterwards... as a suggestion anyway.
Sensor Drone (someone can name it. I suck at names
)
Drone-class
Armor: None
Weaponry: None
Engine: Simple, but effective (mostly deployed from a ship before slowly moving to designated areas.)
Other Systems: Sensor intensive, along with inter-drone ai communication.
Description: Cheap early-warning drone to alert merchants of danger to avoid. Emphasis is on cheap but effective, especially as replacements will be required as pirates will eventually start targeting them. Only ships with the right codes are identified by the drones as friendly, with the code itself hard to hack. Outer layer is ceramic with an inner layer of plastics. Drones ai interlink with each other, making it possible to get a larger picture.
Suggested Use: Deploy along the important stretches of trade for the planet, along with selling to other merchants that could benefit from it.