Why torpedo tubes complicate a hull

Could underwater torpedo launchers use a partially trainable mount, or could more launchers be placed in the bow?

They are possible, but the extra firing arc must be weighed against below-waterline sealing, hull complexity, vulnerable internal volume, and disruption of the bow form.

A submerged or partially trainable launcher adds machinery and openings below the waterline. Its moving parts must preserve a watertight seal while remaining maintainable after damage. A bow installation occupies the part of the hull that most strongly shapes movement through the water and can face severe structural loads when damaged. The wider firing arc therefore costs internal volume and hull-form efficiency while adding sealing risk and harder damage control.