Why Renown did not need ten torpedo tubes

Could the Renown class have been built with ten torpedo tubes?

It could, but there was no sound reason to make torpedoes a primary feature of a battlecruiser.

Feasibility depends on what mission the extra tubes would serve. Capital-ship torpedoes provided a last-resort option when a battle closed unexpectedly or a crippled enemy came within range. Making them numerous enough to shape the design would turn a secondary precaution into a primary armament. That trade would consume space and attention better spent on the guns, speed, protection, and endurance that defined the battlecruiser's role.