I've thought about this myself a few times. What I actually do is find the photo of the commander who actually had the boat I'm playing at the start date I'm using. I just copy it into SH3 commander. I use their actual names, too.
I hope I'm not stirring up any unhappy ghosts from Davy Jones' Locker.
But I think I'm fairly safe...I have the utmost respect for all those U-boat commanders, and I have a decent appreciation of the bravery they displayed and perilous situations they had to deal with. Those guys truly had balls the size of planetoids.