There isn't an officially planned list, most characters will have their own scenes (such as Amora's interrogation scene) -- though characters like Leslie and Shaleus are planned on being two of the Captain's "main" choices.
As far as alternate outfits go, they're mostly going to be restricted to their own quest-line. This game wasn't built with alternate outfits in mind, so instead there will be certain missions that require certain outfits -- for example episode 2 will take place in entirely different outfits for each of the characters for the entire arc.