(I've done a lot of coding and spriting for this, but I must defer to those more experienced with the balance of the game to design mechanics)
Locked in an eternal civil war, the Yin are one of the most technologically sophisticated powers in the Galaxy, though they rarely involve themselves in the affairs of others. Their organic forms are little more than wriggling masses of nervous tissue with a flagella, but they inhabit a wide variety of synthetic shells, their "bodies" being anything from small combat drones to entire starships.
While reluctant to involve outsiders in the War for fear of unpredictable escalation, one faction has seen a temptation too great to pass over: The NSS Cyberiad. Seizing control of the station and its assets would grant them an excellent production facility for their efforts against the others. And no outsider would know which of the myriad factions to retaliate against.
Mechanics
The Yin start in critter form (outside their shells) on their ship
One will then enter the empty control core in the center of the ship, enabling them to control the ship and its machines, and coordinate the invasion effort. The Yin will then use the Shell Fabricators aboard their ship and plan their strategy.
Shell Fabricators
These print out mechanical shells for the disembodied Yin to pilot (and perhaps items or upgrades). These draw from a point pool (similar to TC stations), which might be static or might be replenishable by loading in more resources. There are two kinds of shells to print:
Invaders, a borg-like, heavily armed and armored shell for overt tactics
Infiltrators, a humanoid shell for stealthy tactics. Possibly starts with implants, possibly spends points to print additional implants/equipment
Yin can eject from their shells at any time, and while in critter form they can ventcrawl. Their organic forms have a bluespace uplink implant that enables them to communicate with each other at any time.
Objectives
The Yin seek to claim the station as a new production facility for their war effort, seizing control of all it's assets (including the crew). To accomplish this, they must:
1) Install a Bluespace Shield, preventing BSA fire from hitting the station or its vicinity
2) Take control of the station's systems by subverting or replacing the AI
3) Prevent their new slaves from escaping
These really need a lot of work.
Unique Equipment
Not that many yet, and not sure about these.
-Morphic Disguise: a programmable disguise for the Infiltrators. Customize your false appearance then slip it on in the mask slot
-Armblade/Armgun implant: a weapon for Infiltrators to use. Not overly powerful
-Guns: Probably mostly energy based. Considering giving their weapons a plasma focus
-Yin Neurotoxin: Causes victim's brain to mutate into a Yin, exploding out of their skull. Probably not as an antag. Won't have the uplink implant (Probably not using this)
-Yin Nanoplastic: transforms the victim into a walking meld of flesh and machine, enslaved to the Yin controller.