Sienar Fleet Systems is one of the four Corporations in the mod and allows a cost and build-time reduction to specific ships and Vehicles only on the planet that the Corporation is built at. This Corporation can be built on the planet Jaemus and is available only to the Pentastar Alignment.
These are the space units that are affected by the Sienar Fleet Systems Corporation:
These are the ground units that are affected by the Sienar Fleet Systems Corporation:
The planet Jaemus suffers from not being in all Galactic Conquests maps that feature the Pentastar Alignment, meaning Sienar Fleet Systems is also not in all GCs featuring the PA as a playable faction.
If Corporations could be made by the other Factions, it is possible for the TIE/D Defender to be affected by the price/build-time reduction bonus supplied by Sienar Fleet Systems as it is part of the TIE production line. But the Defenders part in Grand Admiral Demetrius Zaarins coup against Emperor Palpatine may also be a reason for this not to happen.