Affecting land battles might be over the top. However, depending on the year and month, some convoys could be somehow linked to historical battles and deemed more important.
I've just finished a post about the recognition manual. In it I've noticed that the TDC had a Ship Length dial and so the captain might have had a way to calculate the ship's speed through the TDC. Think about it, with such a tool and a double split prism stadimeter... how long would it take you to find all the data you need (speed, range, aob)? If the AOB dial would be linked to the sub's compass, then in less than a minute you'd know everything about your target and maneuvering for a good shot would be child's play. It would be realistical, but also almost "shoot-em up". The two ways of playing can coexist very well in the same level of difficulty. My feeling is that difficulty should consist of other factors, like escort strength, ai sensors, ai adaptability, torpedo faults and so on. The attack itself might not pose enough of a challenge to differentiate between easy and hard. But the approach, the tactical part, would. That's what being a captain is all about, right?