German destroyers lacked the endurance for a British blockade

Could First World War German destroyers escort battlecruisers far enough to blockade Britain after a German naval victory?

No; their endurance was inadequate, while Royal Navy submarines could reach the operating area and interfere with the attempt.

The escort problem is governed by fuel and range rather than only combat power. German destroyers could not sustain the distant operation, and British submarines retained enough endurance to threaten the battlecruisers and disrupt any blockade force.