Subs yes!
Subs Should be picked by players, so Spies can not see them on the Map. Subs should have spawn points like Pt boats, only more and spread out.
Subs would have to be landed and Victories would be tallied in tonnage. You would also have to have Merchant fleets that sail from port to port. Sinking these vessels would hamper supply operations for the enemy, and slow thier offensive or defensive operations.
Destroyers would also be added and could be launched from ports, or could be detached from the convoy and Task Forces.
