Add me to the list of "not seeing a need for new ships" people.
A ship in Guns of Icarus is essentially the same as a "class" in class-based multiplayer games. We already have more ships than most such games have classes. A lot only have 3 classes.
Light "Scout" characters are covered nicely with the Squid, and the Goldfish can touch on this class in many ways. The Spire is less mobile than typically expected from this class, but can fill a sniper role that's usually filled by Scouts or Scout-equivalent classes.
Assaults are the usual Medium class, and are often either frontline brawlers or flankers. Many Goldfish loadouts fill this role better than the Scout class above, while Junkers and Pyramidions are best listed here too.
The Heavy class is epitomised by the Galleon, but the Mobula fills a less tanky version of the role too. The Junker can be seen as a Medium/Heavy hybrid much like the Goldfish is for Light/Medium.
If you look at various specialist classes, or the sub-classes that can be fitted into those broad categories, you can fill almost every type of role with the right loadout on at least one or two ships.
Shotgunner/melee: Carronade Goldfish, Pyramidion, Carronade Squid.
Sniper/fire support: Spire, Artemis/Mercury Mobula, Several Galleon loadouts.
Area Denial: Galleon with Carronades, Minelayer Junker/Squid, Flamer Squid.
Medic: NOPE, and with this game's mechanics, we're better for it.
Pyro: Ever seen a Junker loaded up with Flamers on both sides and a Rocket Carousel on front with Incendiary ammo?
Demo man: Galleon with quad Hwachas and Rocket Carousels/Mines. Or Mine/Rocket Junkers. Or a Goldfish with Hwacha and Mines.
Weapons, on the other hand... I can see room for at least a few extras, although I don't want this to turn into your average military shooter's weapon selection where there are 1289 different guns, but they're all just sniper rifle, assault rifle, SMG, pistol with different damage per shot, fire rate, ammo count and reload time. The guns we currently have are all unique, powerful in their own way, and very distinctive. Anything new would have to fill a definite new role, or would have to be a Heavy gun filling a role that's currently only covered by Light weapons.