After reading many suggestions, and many of them very good, I'd like to comment. Knowing this is really a "question for the devs" thread, forgive me for commenting rather than questioning, but I can't help but voice this.
The ability to move freely through the sub is certainly going to be entertaining.....at least for a little while, until we've roamed the boat a certain number of times and heard all the scripted lines the crew has to offer and will be ramdomly using. After a while, and once we have heard all the possible lines the crew can give us (such as the cook asking if we wnat to sample the days menu) I fear it will become quite boring and we'll all go back to keystroke navigation between compartments as we've done all along. Still a nice touch though!
The idea I've heard that sounds most intriguing is true navigation. Now that's a true simulation! While I'm the one suggesting (earlier in the thread) an option to RTB once out of enemy territory, if we could navigate like a true sailor, I'd find that to be a challenge on it's own, and it would certainly take a lot of boredom out of that long trip back home. It would throw in a whole new learning experience for most of us. Not to mention, imagine us having to ease off the time compression for a change. We'd be forced to keep an eye out for landmarks to avoid running aground or crashing the boat , or better yet, and most importantly....
confirm our location. Imagine the satisfaction of navigating across the ocean with much anticipation, and then discovering a landmark confirming you are where you had hoped to be.
What a thrill! I would find that more rewarding than sinking the Yamato, Bismark, Enterprise or whatever any day.
I realize many (maybe most) players will not have the patience for this and those not desiring to do so, could use the "GPS" option. But man! It would open up a whole new facet in the game and take it to well..... again, a real sim. This would be a fantastic selling point too!