Here are some ideas i have be thinking about first
Is that Officers have abilities like a boost ships or fleet speeds or attack or whatever
my next few are voodoo
Summon a ghost ship- cost 10 rare- summon a ship, ghost ships can not be attack with holy cannon but always have +2 danger rating and kills non ghost crew one a day ghost ships can attack by ghost ships

summon the dead- cost 6 uncommon-it summon 25-40 crew, ghost crew can not be fire with out Exorcism they will deal Damage to the a non ghost ship 5% a day

Holy Cannon- common cost 3 24hrs you can attack ghost ships

Exorcism- common cost 3 fire all ghost crew on a ship

I hope you like this ideas