Made those illegal modules rare, like there are only 100 modules per type
The idea is that each new mission will introduce something new in it, to keep in line with the exploration / mystery side of things.
Those modules will have a chance to spawn in the cargo bay of the pirate station, and part of the mission reward will be used to get sort of like a ticket, that gets you a chance to spawn this module, so they will be rare and expensive.
To give an example, let's say you have a mission usually pays 100k solars. Now from that 10k solars goes to a kind of a lottery, that if won will spawn a module worth 500k solars to be looted. You won't see those tokens, but that's how it works. 10k/500k gives a 2% chance, and higher tokens, as you fight more enemy (this ofc depending on the power of the ship taking the mission and mission difficulty), could yield a 500k or higher mark module. So if you have higher value tokens from higher diff missions, so your chance stays within same lower ranges, but you get a chance at higher mark modules.
This is of course just the beginning of a platform that will form the basis for looting rare modules from the vicinity of black holes, that will be left by exploding stars, worm hole explorations, archeological sites and etc. Those modules will be rare and expensive and provide unique bonuses, artefacts of great value and markup once the SOL auction system goes live.
So every new mission will come up with something new in it, different from the other. The "Pirate's nest" mission will have different reward then the "Pirate Hijacker", in a sense that it will pay part in solars, part in station loot and part in rare modules that not every mission will spawn, but when it does, the treasure will be worth much more then that mission reward.