There was this engine failures in SH 2, and other problems as well. Is it this kind of failers you wish should be simulated in game?
About torpedos, have you tried TII's early in war combined with checked for dud torpedos in options? My experience is that they fail more often than they works
For realism, in that case there should be a progress of mailfunction. There where more failours in early war than in late.
And I think thats the case with the TII's but Im not sure.