I mean, we could not nerf, rather strengthen other ships.
I second this:
Squid: Angle the starboard gun more towards the front, allows for more combination and usages.
Mobula: Balloon buff, Velocity buff
Galleon: Needs to be more enjoyable to fly, right now you can't see anything from the cockpit, it isn't maneuverable and isn't fast either.. Overall it is just boring to fly.. not sure what is within your limits to change.. maybe move the pilot seat? But I'm not sure, firepower wise it is balanced and good and does it's job well.. just no fun to fly imo. Maybe a balloon buff would make see more action? Or a buff to it's guns angles (Hwacha vertical angles)
Spire: Movement speed buff.
I also think the Heavy Carronade needs a nerf or a Junker balloon needs a buff as as it stands the Junker is very easily countered and therefore is very unlikely to be seen. (Edit: As a core ship that is, it is still sometimes seen as a support ship)
Anyway, this is just a short draft of my ideas.. feel free to comment and criticize!