If it's about the characters, what do you need a spaceship for? It is a simple truth that people are what they are becauee of their environment and act the way they do because they are carrying out social roles suitable to it. Science fiction as such rather conflicts with realistic characterization.
If it's about characters having bad ass moments and vividly presenting themselves and changing in a satisfying way? If it's about heroes suitable for vicarious fantasy? Then there have to be victims, sidekicks, admirers, satellites, characters who do the unpleasant stuff.
The best example is the much abused Harry Kim. Kim was a token Asian mainly. But insofar as he was a character he existed first to service the Tom Paris character. In The Caretaker, Non Sequitur and The Chute his role was to be saved/redeemed by Tom Paris. And the rest of his function was to do the unpleasant stuff, like wanting to go home or being otherwise flawed, as in Favorite Son or Nightingale. The Kims have to be written so that there can be episodes or scenes that aren't about badassery.