I would like to see a situation where the player is forced to use his ships to protect a paticularly valuable cargo from piracy or privateering. Say Spain defending her gold fleet as it sails from South America.

This would result in a battle where you not only have to defeat the opponent but you also have to protect the convoy. This sort of objective has never been seen before in a Total War game. It would be possible to annhilate the enemy but still lose your gold ships, thus losing in the long run even though you won in the short term. An interesting tactical challenge that adds a little variety into the game.

Of course the reverse would also be true. Maybe use a fleet of small but fast ships to sail through the enemy line of battle and sink a treasure ship or two? Or maybe use a heavily crewed boarding ship to steal some gold then flee the battle before the sluggish First rates can react?

To me it sounds like fun.