First is the whole water problem.
Second is the time issue, bad enough with GV's that move at 20+ mph.
Sub's submerged moved at 4 - 6 mph.
Third is the fun one, how the heck do you model sonar?
And yes it has to be modeled on both sides in order to have an effective sub.
Boxed games use time compression for #2, canned response's for #3.
Neither of which will work well for AH.
I could be wrong, but as I see it those are just the first 3 biggest problems.
Then you have to somehow model a periscope, slow down the Task groups, deal with refueling, rearming issues. (or the task group can run at 40 knots endlessly)
Its a big job, and I suspect HT has a limited amount of time to "play" with it.