Could a larger, 'super Royal Sovereign'-type battleship have been built?
Short answerTheoretically yes, but only once advances in turbines and naval architecture made a much larger hull structurally practical.
NotesA larger Royal Sovereign-type battleship was possible in principle, but ships could not simply be scaled up without supporting engineering. Longer hulls required advances in naval architecture and hull construction. Turbine machinery formed another part of the technological change. Dreadnought arrived when these developments made the larger ship practical.