I've been reading a bit more about war at Sea during the Punic Wars. Storms were more "decisive" than the naval battles. Rome lost several large fleets to storms in the first Punic war, despite being very successful in actual naval combat. The Carthaginians fared better weather wise because they were more experienced with weather at sea.

Boats in port were generally protected. Wouldn't it be nice if all those lovely stacks all over the water were subject to frequent destruction by storms? It would be nice if there were something to encourage boats to stay in safe waters except when launching some sort of attack or defense. A mission based approach to naval warfare would be interesting. The AI would have to be programmed to work with a new system.

In battle or storms losses should primarily be loss of the boat, not just fractions of the crew.

Additionally, it should be much more challenging to move armies by sea. 1 unit of infantry per boat (actually they would probably be towed) and probably 2 boats (or 3) per cav unit. Cav was logistically difficult to transport by sea.

Blockades would be more challenging if it took some number of boats to conduct them and depended on port level etc...not just a single unit. With that the AI would need to get instructions to actually use those fleets.

And the grouping of admirals bug would need to be addressed as well.

Oh well, fun to dream...