This looks fantastic!!!
Not had a chance to play it yet, just thought I'd quickly say that Google chrome is blocking the download!
Edit: HOLY HELL! Your new project sounds amazing! Have you played 'Artemis:Bridge Simulator'? It's a similar idea but in space. I'm a huge fan (and it's very popular in extremely geeky circles) due to it being one of the few multiplayer games which is actually cooperative rather than just sort of 'shooting the same bad guys'. Worth a look at to learn from it's successes/mistakes.
One major thing is that it's one of the few instances where realism definitely needs to be sacrificed for game play. Artemis has a bit of a problem with some 'stations' being pretty boring - because as important as they are, they're just not that exciting to play as. Now on a sub, that problem is going to be amplified, as there's less lasers and more checking. No one is going to want to be in charge of being sat checking the air mix - no matter how important it is.
I'd suggest you either get around this via making it slightly 'futuristic' with a lot of things automated, or having each player character assigned to be the officer for a department (engineering, weapons, and so on) - however the second option might feel not 'hands on' enough for some people. 5 people is definitely the sweet spot for number of players, although it's always good if it can be scaled up (so if you've only got two friends, everything will still work).
If you'd like some more in depth feedback as a long term player of Artemis, do let me know.