I found leaving and entering the harbour quite boring in sh2. After sinking loads of tonage i want to be greeted back at home port.
I think having ports with U-boats and shipping comming in and out, would make it allot more interesting. You could have boats sent out to escort you back into harbour, maybe even include the U-flak boats for air protection.
Also how about leaving the harbour with other U-boats, or did they not stick together leaving the harbour incase of air-attack?.