I think for the most part in actual gaming the player isn't going to encounter too many sitting targets, so acceleration from zero or one knot probably isn't as much of a concern as acceleration from 6-10 knots for merchants and 10-15 knots for warships.
Another thing the game doesn't take into account is the Pearl Harbor syndrome: ships that are at anchor have a very good chance of being in a steam-down condition. It doesn't matter how soon they spot the torpedo - that ship isn't going anywhere in the next hour or so.
The work you're putting into this problem is very much appreciated.
