Missed one,
"Can't tell you how often I've had a leak and had to keep ordering depths just to keep from sinking too low or slowly rising too high..."
Too often. E to blow ballast, then P for periscope depth rising past 100 feet to avoid broaching in the middle of 6 destroyers, waiting for it to sink back down to 300 and blowing again, lather rinse repeat.
Until you run out of compressed air. Flooding in the after torpedo room so the stern is down, it WILL stay at periscope depth but with the periscope 30 feet underwater and the bow sticking up 40 feet above the surface. No way to trim by pumping from after trim to sea or putting a bubble in some of the after ballast tanks. This game gives the impression that there's one ballast tank that's either empty or full, and no such thing as trim tanks.
Just the ability to compensate for flooding to level the boat and/or keep it from sinking would be enough, having emergency blow as the only option is ridiculously simplified for simulating any submersible vessel.
"Just a quick thought here while I have time. Drills."
Second that, every WWII fleet sub article the pundits claim 30 seconds for Das Boot and 60 seconds for US fleet boat. Every account by an actual WWII submariner says 60 seconds for the first few days, but keelhauling for the entire crew if they couldn't get that down to 30 seconds after a couple weeks of drills.
"Having nothing to do besides keeping the time compression pumped up to it's highest level in the two weeks steaming from Pearl Harbor to Japan"
Primary reason I've "Gone Asiatic" and made the mod with the supply bases, that long tedious trek to and from the operating area was just too boring for what's supposed to be entertainment.