[@Narcotic Dollie]

1.  Can the original characters have different genders from the cannon ones? For example, having a female doctor or a male companion (Do those even exist? I don't know.).
A: Yes

2. Would the cannon relationships carry over? Like the pilot and the soldier being married, the mechanic liking the doctor, etc.
A: Only if the player(you) were playing both characters or had a friend join that wanted to be the other person in the relationship.

3.Also, which role would you play? Are you our captain tight pants? :D
A: I thought about that but I would rather be reavers or alliance patrols or Badger.

If this gets off the ground with one key spot missing, then I would NPC someone. If you know of others to drum support then by all means they are most welcome! =)