Thanks for the words of support guys!
You can now muster your crew upon entering and leaving port using ACTUAL crew slots, instead of the modified snorkel I showed earlier.
The snorkel, which has been freed up, can be used for maybe another special event. Like burying dead crewmembers at sea, for instance.
I can also mod in kill pennants if you like, but I would need to replace one of the periscopes to do this; not 100% sure if that is a good idea. It would depend on how much people use both periscopes when playing the game.