I think I'll play my engineer character.

My idea is they were living in a colony that got devastated by the initial conflict and they are one of the few to actually make it out, but with basically no one and nothing left. They were already an engineer but joined up with the military to help in the only way they knew, repairing spaceships and walkers.

They may not have seen much action but they would see the damage and repair and sometimes not see people come back. Eventually they got attacked directly and just couldn't run away when they knew they could help. So they got in a walker and with their understanding of how the machines work managed to really mess stuff up.

Personality wise they're probably sort of like the mom of the group. Was imagining them as a woman but depends on the group dynamics. But sort of protective and caretaker, really cares about the machines and just doesn't want to see any more friends get lost. Probably a bit too naive or sweet for the military. Add a bit of trauma and they aren't the best fighter but aware of flaws and weaknesses in their enemies.