Lütjens commanding an expanded Operation Rheinübung

Would Günther Lütjens still command if Tirpitz and the Scharnhorst class joined Operation Rheinübung?

Yes, and his seniority would make him even more likely to command the enlarged force.

The counterfactual enlarges Operation Rheinübung to include Tirpitz and the Scharnhorst class. Günther Lütjens would probably retain command. A force of that size requires an officer of greater seniority and organizational authority. Lütjens's existing role and rank therefore become more appropriate as the operation expands.