I was thinking Pyras would be pawns since they are first in the fight, there a lot of them, and they die easily. They are also one of the smallest ships.
Bishops are fast and fight by flanking, and you use them to lure your foe into traps, so Squid or Goldfish.
Knights move forward a few spaces then kill from the side, which resembles a Junker.
Spire or Mobula makes a good Rook, since both are known as 'castle' types. Both of them would also make a good Queen due to their sheer amount of firepower focused in one direction over short or long ranges. I would rather see the Spire as Queen, though, due to the size (queen is always the tallest piece), and Mobula as Rook, due to the flat, castle-like deck.
