Could Rear Admiral Somerset Gough-Calthorpe have replaced Beatty instead of Sturdee?
Short answerNo, not as the likely emergency choice. He was still a rear admiral, while the Admiralty had vice admirals available for the Battlecruiser Fleet command.
NotesSomerset Gough-Calthorpe was a rear admiral at Jutland and commanded the Second Cruiser Squadron from HMS Shannon. That rank makes him an unlikely emergency replacement for a vice admiral commanding the Battlecruiser Fleet. The Admiralty had serving vice admirals available and would not need to promote a junior flag officer over them. Formal rank and appointment politics narrow a counterfactual that otherwise seems to offer many capable names.