Why a 24.5-inch torpedo remained too heavy for destroyers

Would a natural-air rather than oxygen-enriched 24.5-inch torpedo have had a better chance of adoption?

No. Its decisive problem was weight and handling, not simply the oxidizer system.

A 24.5-inch torpedo could be effective, but changing its oxidizer would not remove its sheer weight. Royal Navy destroyer crews still moved and reloaded smaller torpedoes largely by manual effort. Applying the same practice to this weapon would be dangerous, so the ship would need powered handling gear and a much larger magazine system. Those additions consume enough space and displacement to make adoption on a small combatant unattractive. Ammunition handling can decide whether a weapon is practical even when its performance is attractive.