You're going to need that aft mast if you intend to do any long range communication. You're not going to be able to string out the type of multi strand aerials (Not the technical term) they used back them.
Also I would expect to see at least some form of "heavy" LAA ala the
Swedish Bofors, the
British two-pounder or the
American 1.1in
Well... how should the mast look? I have honestly no idea, and I've had a hard time finding any examples here on SB.
About the Heavy LAA... I'm actually not entire sure. Those that she uses are supposed to be 0.98"/25mm, fairly close to the 1.1"/28mm that you used as example. Plus, I think it is possible that an early stage 'super destroyer' coul well use such light AA. For example, the Fubuki, if I remember correctly, the first 'super destroyer', of the same era, used 5"/127 mm main artillery, and a LAA suit of 0.51"/13 mm.
So I think it's fairly justified to keep the 25 mm.