Then due to neutrality in World War I, the Dutch army becomes quite incompetent and behind the other civilized nations of the world, and mobilized too late in World War II to put up a good fight.
While the Dutch Army was not able to put up that great a fight, the Dutch Navy in WW2 was on par technologically with the rest of Europe. They were working on the snorkel prior to WW2, and had on the destroyer Isaac Sweers a prototype AA fire control system for the 40mm Bofors gun that the British though highly enough to adopt post-war. Their ships ad submarines were good. In aircraft, they were also pretty good.
Minefields ( on both land and sea. They operate a little like the mines in Escape from Zombie Island. Very useful for killing submarines, although my research revealed that in real life only 3 submarines were ever sunk due to sea mines. They were still a significant enough part of WW1 to be implemented, I feel. )
I would be interested in where you got your information on mines and submarines. The US alone lost probably 5 subs to minefields in the Pacific in WW2, while the British lost several to Italian minefields in the Med during the war. In World War One, mines were quite deadly against subs as well, while the Germans had several of the minelaying subs blown up by their own mines while trying to lay minefields.
As for the AI using curraghs for settlers if they can carry two units, I can vouch for that definitely being the case. I play exclusively on archipelago and continent maps with only one or two civilizations per land mass, and the AI will be very busy sending out settler ships. My basis for curraghs having a capacity of two units is based on the galley having a capacity of two. Curraghs, being primarily sailing ships verses rowed had more cargo capacity than a galley, and could carry about 20 to 30 passengers, on par with a galley.
With respect to ships, you might want to take a look at my naval mod:
http://forums.civfanatics.com/showthread.php?t=322522
I have been working for a while on it, and while battleships could probably be boosted a bit more, they are pretty deadly as is.
Also, with respect to WW2 anti-aircraft fire from ships, you might want think about having some distinction between countries. By 1944, the US Navy was shooting down 50% of all attacking Japanese aircraft with anti-aircraft fire, and for the battleships, it was closer to 90% of attacking planes. The Fletcher-class destroyer would have been rated as an Anti-Aircraft Cruiser is just about every other navy of the time, and that was before the introduction of the proximity fuse for the 5"38. There was one case off of Okinawa were a destroyer on radar picket shot down 22 out of 28 attacking Kamikazes. At the Battle of Santa Cruz in October of 1942, the US Battleship
South Dakota was credited with shooting down 26 attacking Japanese planes while suffering exactly 1 (ONE) bomb hit on B 16-inch turret.
Note: This data is based on extensive research into WW2 anti-aircraft engagement reports which I did for a couple of war game companies in the mid 1990s. I have the analysis in PDF format if anyone is interested. It also includes bombing accuracy verses ships for the Pacific war. Both the Japanese and US naval pilots were more accurate than the Stuka when it came to hitting ships in 1942. Dive bombers and torpedo planes were far better in WW2 at killing ships than horizontal bombers. Do some reading on the Guadalcanal campaign, the convoys to Malta, and the Battle of the Bismarck Sea in March of 1943 for more background. The Bismarck Sea action featured the first major use of skip-bombing by the US.
Be careful making WW2-era bombers too powerful at killing units. To achieve significant success against ground units, especially ones dug-in, required a very large number of bombers attacking a fairly small target area in a very short period of time. Read up on the carpet-bombing for the Normandy break-out to get some idea of what I mean. You can download the official US Army history series from the Center for Military History website.