Yes, I was thinking myself that a hospital ship would be a good addition, and it wouldn't need any structural changes at all IMO. It shouldn't be armed though. Which ship will it be - The Passenger Liner, the Troop Transport, or Serg's Transport? If there was a separate one for Allied nations, you could give it 0 renown so that we're not rewarded for sinking one, although loss of renown might be better.
BTW - Speaking of the Bermuda Triangle, wasn't the Marine Suphur Queen, which supposidely vanished without a trace, found last year? Last I heard, it was yet to be confirmed, as the wreck may have been WW2 era. We don't need to add the MSQ to the game though, she's already there

. (T2 tanker).