The submarine warfare rules are pretty much an appendix for this game- nothing really changes if you remove them completely. Given how important they were to the real war though it’s understandable enough that Larry Harris would have felt it necessary to include something along those lines.
Of course even if a German player wanted to make use of this rule the setup makes it very difficult to pull off just to shave off a few IPCs of income. Unless you are willing to risk the 30% chance of loss just going directly to SZ 8 from SZ 10 then it’s 2 moves to get to the convoy raiding zones, making them too far away. As the weakest unit subs are highly vulnerable without some beefer units around to discourage attack. The German player will likely only have these around at the start of the game meaning the attack on the SZ 9 UK fleet would probably have to be skipped… so maybe consolidate the starting German fleet in SZ 4 as an opener to preserve these ships for as long as possible. It’s also a problem that you cannot do either/or with the UK and USA and just hit the UK’s income until turn 4 unless you want to hit the USA earlier… given that the main impetus for even having this rule to begin with is historical accuracy this aspect of the rule is a bit of a puzzlement.
So imagine that the rules were changed to be the following : any German sub that has not moved and is in a friendly SZ with a friendly port can do the income denial attack on the UK’s income, or on both the UK and the USA’s income if the German player wishes the USA to enter the war earlier. This would allow the German player to attempt this as a strategy with a little less risk. If the German fleet skipped the attack on SZ 9 and holed up in SZ 10 or 11, maybe buying 1 additional sub every turn, the Entente would then be forced to respond and possibly help the Ottomans buy reducing what gets placed in India if the UK buys ships. For those who like having rules mapped to real-world activities, imagine that the subs are based in a home port and use their movement to go out on patrol looking for merchantmen before returning.
Is this enough to make a CP player experiment with economic warfare, or is it still not viable even under these more favorable conditions?