Hans,
you and your friend should consider joining Daemon in his long-term project to build a WW1 UBoat simulation. Basically, the same engine he is developing (With the most incredible and amazing attention to detail and realism I have ever seen -and I have tested some of his pre-alphas) would work perfectly as a WW2 UBoat simulation with just adding the new 3D models you so well develop.
A colaboration bewteen you guys would push the project forward easier, and Daemon's one is also a commercial one, so you could find the income there.
Ask him to send you per PM a dossier about his sim and an outline of his current progress and schedule, you will be amazed
http://www.dreadnoughtproject.org/heinrich/main.htm
Forum here at subsim.com:
http://www.subsim.com/radioroom/forumdisplay.php?f=178
Ignore that the page has not been updated for a long time, work is going on steadily behind the curtains.