I have been a big fan of this mod since day one, so you will forgive me if what I am gonna say will sound a bit heretic here.
In short, I am pretty sure that though an U-boat captain would have known the enigma encoding/decoding process inside and out, it wasnt his duty deciphering any incoming message.
So my question is: how difficult would be for you adding a "Radioman, decode the last message for me" button to the UI? If possible, you could add a random delay of 3-10 minutes between the issuing of the command and the decoded output, depending on the length of the message and on the training/morale of the radio operator. And, of course, if the radio man was injured, the said button should be greyed out.
Imho this feature and the automatic message encoding that I was talking about a few days ago (needed for the correct encoding of campaign orders based on their variable issuing date), would further improve your amazing mod, and provide the perfect compromise between casual and hard-core playing styles.