May seem like a small thing, but I feel it is important to move away from the ramming / point blank torpedo strikes that are a bit silly, and take out capital ships too easily.
Torpedos should not arm until they have been in flight for a set duration. This is mostly a gameplay issue (see above), but also makes perfect sense, since the firing ship does not want the torpedos to detonate too close to itself.
Interestingly this also leads to the possibility for having different torpedo types, with flight speed, arm time and damage being different.
A visual indicator for when torpedos have armed would be a nice touch, allowing the tactic for flying towards and into the torpedos BEFORE they arm, and also giving players a chance to see why torpedos do not detonate sometimes. A flashing light increases in flash frequency until it goes solid (armed), or something like that.