It has occurred to me to, if nothing else, have a patrol or two that involves cruising around the Bay of Biscay until January of 1941---a grand total of about three weeks---and then starting from there. Call it the U-48 Farewell Tour or something.
I may yet be forced into this one, but the good news is that I can easily do it thanks to preserved saves. I'll just have to make the manual changes to the crew via SH3C.