Hi, Darrians tend to use TL 13 ships (as noted in their supplement) and are currently having their ships replaced by TL 15 Imperial-built ships thanks to trading technology with them.
TL 16 ships exist, but these will be the Ancient Relic ships the Special Arm will be sent after, or that they pilot themselves.
Also, Special Arm go about in demilitarised TL 16 merchant ships to hold the Star Trigger, with the dimensions given for a Trigger when the Maghiz happened, you'd need a Capital Ship sized Cargo Bay so these kind of ships are only good for Bases for the characters in your games really, who are escorted by a TL 15 fleet and perhaps one or two of the found TL 16 Relic ships.
If its a free trader game youre looking to do a ship for, just find a ship thats TL 13-15. The Darrians supplement ships are all TL 13 and fine to start a game with.