There are several repaints available ryan, in fact there is one of the first repaints ever done for SH3 by 'yours truly' for the VII available on the Subsim SH3 Downloads page, and still quite a nice one I think.
Whilst it is certainly true that repainting meant that there were often not so many rusty boats about as many people might think, one of the reasons I did that repaint you can find on the SH3 DL page, is not to emulate the rust, but to emulate the skin rippling that well-used Atlantic boats ended up with, which they carried even when repainted.
Have a look around, there are plenty of repainted skins available, and one might be what suits your tastes, but there's nothing wrong with a shiny boat in my opinion. Of course after being battered in the Atlantic for many weeks, most boats are going to pick up some rust, but remember that the Kriegsmarine submariners were an elite force, they would not have been content to ride around in a rusty bucket for long, especially when their lives depended on that boat.
Chock
