OK, so here the *real* response goes...
Firstly, for most of this response, other than citing what I will from the original Dev Diary, I'm using Jane's Naval History of World War II. Its more than adequate I feel for covering every aspect of the naval side of the war, and if the Devs have not yet read it, I would suggest that they do so.
1. Please allow me to say firstly that this game looks amazing. I'm loving it, the map, the convoy system, everything. I feel like it addresses much of the shortcomings of HOI2, and even bringing some great new ideas into the game that I feel are just great.
2. This (in conjunction with several other players on this forum who have already stated their trepidation) however, is something that I feel is still needing some refinement. I understand the need to balance gameplay with historical realism. I understand that no everything can make it into the game.
3. The problem as I see it is the fact that the system is pretty much entirely focused on the European Theater of Operations (ETO). The convoy system, the wolfpacks, the submarines, the concept that one unit of subs is equal to approximately 3-6 individuals... its a bit off for my read of what happened. True: wolfpacks are the standard guage for the Germans, and the UK wasn't really interested in the submarine (aside from their use in supporting the battlefleet), and the USSR didn't even bother with much of a fleet at all until after the war. The French... well, duh, and the Italians, while contributing their extensive submarine fleet to the Germans; they were the only other major power to lose more boats than the Americans did, and were much more effective in the Mediterranean.
4. However, neither the Americans nor the Japanese were into the wolfpack, and the submarine war in the Pacific was quite different. Not only was the submarine war different, but the entire convoy system was handled quite differently. That is the focus of my response.
A. American and Japanese submarines were built much larger than their German counterparts... they had extended areas over which to patrol, their training designated that the primary targets were the elements of the other's battle fleet, and centralized command was never considered due to the massive amount of radio traffic (something that helped the British and Americans defeat the Germans). They operated independently, although assigned to squadrons centered around a tender (usually called a SUBRON, for SUBmarine squadRON). This raised the question in my mind of the naval ship tech that the US starts with in 1936, although, the S-, R-, and Si- (S improved) classes were of longer range than their German counterparts. Japan does start with these boats available. The American improvements from lessons of the German boats captured or sunk in their waters were incorporated in the new GATO-class (sometimes called the TAMBOR-class), initially ordered in 1940, with initial fleet units coming online before DEC 1941. The follow-on class, the BALAO, also included improvements needed from the operational proceedures. (BARRACUDA-class is designated class name in the game, but that's something that is so small a nitpick that I could overlook it)
B. Japanese Naval Planning never took into account the fact that it faced a similar situation as the British did, nor did the Americans take into that fact in their Plan Orange. The Japanese did not feel like the Americans would join the allies in recovering colonial possessions, nor would they attempt to recover the 'financial liabilities' of Guam and the Philippines.
C. Japanese merchant building was reduced pre-war to leave yards free to pursue naval contracts; they also deemed that repart and salvage would be sufficient to maintain their imports and exports. Not to mention that their naval resources consumed the slips for their own repairs and refits, while damaged merchants were simply allowed to founder. The Japanese refused to appropriate their ships into convoys: it was a 'defensive' tact, not 'offensive,' and their offensive drive would obviate the need for convoys. They also failed to produce dedicated escorts in any great numbers, again, the defensive nature was subornned in favor of offense. Convoys, when necessary, were usually operational, such as the reinforcements of Guadalcanal, but the convoy as discussed here was not implemented until late 1944, and by then, that just gave American submarines ample targets during their patrols.
Because of the above reasons, I would the following questions: Because of estimated AI programming, how is the 'offensive doctrine' of the Japanese going to play out in the convoy war of the Pacific? What about US production of submarines or their employment? Obviously, as a human player, its going to be necessary to construct subs in order to choke the Japanese, but how quickly will the AI learn?