I wont debate most of your points, Kirkhill, but this one seems rather incredible to me.
Open bridges were the norm of the time. All RN escorts, be they destroyers or cruisers, had open bridges, and it was totally for visibility reasons in action. Even most battle-cruisers and some battleships had open bridges. Only aircraft carriers all had fully enclosed ones. in Canada, we actually had open bridges until the last steamer retired with the arrival of the Halifax class. Classic case was HMCS HAIDA's bridge if someone wishes to see what it looked like. Anyone who served on the steamers (other than the Mackenzie's) would feel perfectly at home there.
So, I can't possibly see this has having been a debate when it came to the Corvettes.