That's a bit more specific than I care to get, seeing how different people's ideas on "realistic" can get. Also people's ideas on "must haves" can vary quite a bit as well.
Instead I will just refer you to this thread, and perhaps you can choose what you think will work best for you.
http://www.subsim.com/radioroom/showthread.php?t=170090
The only real "must haves" are JSGME, which lets you take mods back out if you don't like them, and SH3 Commander, which does for your career what GWX does for your game.