Well, here's something I threw together in about five minutes...
Now, it did crash as it was loading the mission, but I probably forgot something on the submarines themselves, or one of the other files. That was just a quick Flotilla, CareerStart, PatrolObjective and one mission assignment edit. I am almost positive that jhapprich or some one of the boomer modders did this already. You just have to date things specifically, even little things you never notice. You cannot use NULL. It might be that they fooled the "calendar" in the game and made it look like it was 1952 instead of 1942??? dunno, but someone has already done it, unless I was dreaming... ??