Since it’s more likely that the devs will add more careers than more characters, let’s smack up some realistic ideas for fun.
Saltzpyre goes Warrior-Priest and gets a Holy Hammer and Shield as a new weapon, exclusive for the career. However, the Warrior-Priest cannot use gunpowder weapons, which includes the Rapier. I image him being a support and tank, having protective talents that grants everyone more defense in some way. His special ability would make the team immune to damage (not to being disabled though) for a very short time.
Kruber becomes an Outrider, and receives a sabre as a new weapon. Realism aside, it’s a specialized anti-armor weapon. His role will be a hybrid melee/ranged, where doing one slowly grants bonus to using the other. He’d be more focused on dodging and moving than eating damage. His special ability is to use his grenade launcher and blow stuff up.
Elfie gets a more tanky class as an Eternal Guard, with a Spear and Shield to match. Her ability would allow her to avoid attacks for a few moments. She takes the role as a tank that improves the movement/ability to for the team.
Sienna gets a oddball career as a Gold Order mage that practiced Bright Order magic in secret. As a result, she has Gold Order talents and abilities, but still uses mainly fire. Her ability would cause all team members to be protected with a reactive armor that explodes towards the assailant when they’re struck, and her new staff would fire liquid metal that slows enemies for a bit, or something similar.