The Russian capture of the German Naval codes and their subsequent use by the British should be included as a special event. The capture of these codes, and others, should be random and the possibility of no capture or compromise should at least exist. Any movement of the German High Seas Fleet should be known to the AI or human Entente player when it/they are plotting their turn once the codes are broken. The cryptanalysis and code breaking capability of Room 40 British Naval Intelligence personnel would have eventually done the job in any case, as they did with the various German Diplomatic codes. From at least early 1916 any special event allowed to the German player should be known to the Entente player when it is presented as an option for play to the German player.
The possibility of Germany capturing British Naval and/or Merchant shipping codes via a random event should also exist should Germany capture a British warship or transport. Their code breaking capability being not less than that of the British or of the Austrians to read Italian encrypted messages for that matter.