Could HMS Defence have changed Cradock's position?

If Cradock had HMS Defence, would that change the case for the proposed cruisers?

Only at the margin. A stronger force might have helped Cradock, but later battlecruisers were too large to match in numbers, so a smaller deterrent for commerce protection still made sense.

HMS Defence could improve Cradock's chances without solving the wider cruiser problem. The earliest battlecruisers were close enough in scale to armoured cruisers that navies could choose between the two types. Hood, Renown, and Repulse were too large to build in the numbers needed for trade-route coverage. A ship of roughly 15,000 tons could deter a battlecruiser used as a surface raider while remaining practical for commerce protection. HMS Defence might strengthen one squadron, while the proposed cruiser addresses the fleet-wide need for numerous ships.