Here is my theory on naval combat and the way I'm going to play random maps:
Curraghs upgrade to Caravels which now should be 0-2-5 and carry no units. The Portuguese should get a 2-2-4 caravel that carries two units. Galleys should upgrade to Galleases which would have indentical stats to the original Caravel and they would still upgrade to Galleons who still upgrade to Transports. The Caravel would upgrade to a PT-Boat and there should be two cruisers, and anti-air one and a cruise missile launching one. AEGIS Cruisers should be able to launch cruise missiles and take down aircraft as should Destroyers, at least with the cruise missile launching thing. Battleships should have lethal sea bombardment and should be much more expensive and powerful. Nuclear Submarines should carry 10 units and you should be able to capture Battleships, AEGIS Cruisers, A-A Cruisers, Cruisers, Destroyers, Submarines, Nuclear Submarines, Carriers, Frigates, Men-o-War, and PT-Boats in port but not Light Gunboats, Ironclads, or Galleons. Oh yeah, and Carriers should carry 20 units and Frigates should upgrade to Battleships.