Could more Tribal-class destroyers have filled the roles of Leander- or Arethusa-class cruisers in an emergency?
Short answerThey could cover part of the work, especially alongside Dido and Arethusa cruisers, but they would function as elements of a wider mixed force rather than exact replacements.
NotesMore Tribal-class destroyers could have covered some work otherwise assigned to small light cruisers. Tribals frequently operated with Dido and Arethusa cruisers, making the substitution most plausible within a mixed force rather than as a one-for-one redesignation. Treaty limits constrained Royal Navy construction, while Australian and Canadian orders added related hulls and later Battle and Daring classes continued the large-destroyer path. Substitution was a force-structure option with timing and alliance dimensions, without making destroyers and cruisers identical.