Trying to think of a new hero option, one could be a water-specific hero.
Possible bonuses:
-Water Terrain Morale (or Fear if Pirate): Maybe this is only for units in boats
-Plus movement for boats
-Cheaper boat upgrade for units
-Commander/Pirate ship option that would be an even higher boat available (increase max strength/movement)
-Ability to navigate the top boat option through any water (open seas/shore)
-Good pillaging (especially if Pirate)
-Starts with good UL but caps out at mid-levels (so that it will be hard for level 3 ruins)
-Good view range in boat