The reason why electrics were not carried externally is due to the fact that the batteries required regular recharging, to top them up. If they were stored externally, the batteries would run down; I'm not certain how durable they were or if they were "deep cycle" batteries, but allowing them to run down was probably a concern. Electrics, like steamers, also required regular maintenance. If they were already in the tubes, they would be hauled out, worked on and then returned. Items like batteries and compressed air flasks required check ups; if the ship had endured close depth charging, the torpedoes would be pulled and checked for damage to more delicate mechanisms like the gyroscopes and depth keeping hardware. These concerns are not modelled into the game.
My own practice is to never store electrics externally and to do away with them when Allied air cover makes their reloading problematic or practically impossible, like the deck gun.
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