I like the idea of Ironclads becoming an ocean-going vessel and I think the Torpedo Boat works well as a the new industrial coastal defense boat. It does mean quite a long gap between the Galleass (early Renaissance) and the Torpedo Boat (mid-Industrial) but I don't think it's a major issue. I found some Torpedo Boat art, I think it's Hungarian (Elster?) but it looks vaguely similar to the
1876 HMS Lightning. I don't there's really room for any sort of Pre-dreadnought ship, that role is already well covered by the Cruiser and the era just doesn't last long enough to fit more in.
Here's my first attempt at scaling the stats of naval units a bit more smoothly:
Galley: Str 2, Move 2, Cost 50, Cargo 2, cannot enter Ocean
Trireme: Str 3, Move 2, Cost 50, cannot enter Ocean
Dromon: Str 5, Move 3, Cost 60, cannot enter Ocean
Cog: Str 3, Move 3, Cost 60, Cargo 2, cannot enter Ocean
Caravel: Str 3, Move 3, Cost 60, Cargo 1 (special)
Galleass: Str 8, Move 3, Cost 70, +50% Coast attack, cannot enter Ocean
Galleon: Str 6, Move 4, Cost 80, Cargo 3
Privateer: Str 10, Move 4, Cost 90, hidden nationality, can attack without declaring war
Frigate: Str 12, Move 4, Cost 100
SotL: Str 15, Move 3, Cost 120, 8% bombard
Ironclad: Str 18, Move 3, Cost 150, 12% bombard
Clipper: Str 10, Move 5, Cost 100, Cargo 3
Torpedo Boat: Str 18, Move 4, Cost 150, 1 first strike, +50% Coast attack, cannot enter Ocean
Cruiser: Str 30, Move 6, Cost 200, 16% bombard
Transport: Str 16, Move 5, Cost 150, Cargo 4
Battleship: Str 40, Move 5, Cost 240, 20% bombard, 60% collateral damage
Destroyer: Str 24, Move 8, Cost 200, 30% Intercept, can detect Submarines, +50% attack vs Submarines
Submarine: Str 24, Move 6, Cost 180, holds 3 Missiles, can detect Submarines, 50% withdrawal
Attack Sub: Str 30, Move 7, Cost 220, Cargo 1 (special), Invisible, can detect Submarines, 50% withdrawal, +50% vs Submarines
Missile Cruiser: Str 40, Move 7, Cost 280, 20% bombard, 60% collateral damage, holds 4 Missiles
Stealth Destroyer: Str 30, Move 8, Cost 250, 2 first strikes, stealthed, can detect stealth ships
Upgrade paths are:
Galley ---> Cog ---> Galleon ---> Clipper ---> Transport
Trireme ---> Dromon ---> Galleass ---> Torpedo Boat ---> Destroyer ---> Stealth Destroyer
Caravel ---> Frigate OR Privateer
Frigate/Privateer/SotL ---> Ironclad ---> Cruiser ---> Missile Cruiser
Battleship ---> Missile Cruiser
Feedback welcome.