Actually the majority of German subs sunk were from hunter-killer cv groups. These cv's were much smaller than the types that we have in this game. The allies invented what the German's called wabos a type of dropped depth charge that was very effective.
I think if subs were introduced that spawn points near ports and bases close to the shore would make the most sense. Catching a cv group in mid ocean would probably never happen. I think they would be of some use for shelling towns, bases close to shore and should be able to carry troops for base takes. The plane carrying versions as mentioned could play a part as well.
Just my thought.
Of 1,155 sent to see the Allies sunk 725 of them. Of the 35,000 brave German sailors who manned the subs 28,744 never came home. Thats a casualty/death rate of 82%. The highest of any service, or activity, in the war.
Also code breaking and the Intelligence war had as much to do with beating the U-boats as did aircraft. The Germans had broken the Allied signals code but then we changed it at about the same time we got our hands on an enigma machine. Now we knew where the U-boats were and since the Germans navy preferred a highly centralised patrol system it proved fatal for the U-boat service.
They eventually built a U-boat that overcame these shortcomings. Unfortunately for them they just didn't have the time, or the numbers of elektro boats, to change the outcome of the war. Enjoy the web site
http://www.uboataces.com/