are these convoy zones like the ones in AAP? that correspond to a particular territory(s)? Then you could cut off Borneo on one turn and take it the next if you had to delay, but you would deny UK the income.
All this is speculation and probably we won’t see any of it in the game. The same effect can be arranged by just moving IPCs from territories in Africa to Middle East and Southeast asia. But the idea would be that a convoy zone lost means that number of IPCs lost for the owning player, so not like in AAE where convoys represent off-map income but rather like transport networks that can be disrupted. Maybe subs could have the special power to fire a shot at a convoy and you then lose that number of IPCs directly, since subs have such poor defence values. Number of IPCs on convoys could be fixed at 5 per country or even better range from 10 down to 2 IPCs depending on how vital sea routes were for each power.
I would really like to allow subs to ignore DDs when moving, it would make for more a chance for subs to be bought by Germany. If we don’t have convoy zones, at least that would mean something more like an Atlantic war.