I think boats should be more modular and quality should matter on how efficient those modules are.
Hyoothrtically the base boat quality would give more slots or higher effiency based on quality and matieral used.
So every 300ql boat is very different and made for different purposes.
For example.
You make a oak base and it gives + 1 inventory row and +1 ruder slot
Or
A yew base and it gets + 1 seat and +1 attacker slot
Or
Pine base and get +1 sail slot and +1 armor slot
In each slot you can add a type e.g. river rudder, ocean rudder, small sail, large sail
Each of these would be better at specific water based practices
Loses passengers for more cargo space
Lose attacker slots for more speed
Add armour for better whaling but worse speed in rivers etc.
The idea should remove the blanket higher ql = faster and better to higher ql improves it's specialisation ability.
Ofc this needs some more design time but it's the general idea.