Well I just finished my first patrol with all convoy routes replaced with zigzagging waypoints (I set all waypoint.radius = 0) and I loved it. For the first time in weeks I missed an entire spread when I fired precisely at the "wrong" moment from about 7000yards out (mk16 torps).
The convoy turned 40 degrees to port when the torpedoes where about 1/3 on their way and they all missed by what felt like miles. It might be easier to find convoys like this, but it's definatly harder to get the kills. I don't know what would be realistic settings for the zig-zags but I used 20degrees and 10miles like your example script.