The reply names small-tube boilers as one way to make the Queen Elizabeth-class battleships more capable. The suggestion belongs to a playful counterfactual about making the class even more formidable, so it is a hypothetical modernisation choice rather than a historical refit claim. The boiler choice is the entire technical answer because the passage gives no performance figures or engineering consequences.
Notable Point · 4:10-4:28
Small-tube boilers for a hypothetical Queen Elizabeth upgrade
A playful proposal to make the Queen Elizabeth class more formidable receives one concrete suggestion: small-tube boilers.