Player character build

[Magic Toast]

Let's say your player character is released as their own unit you can bring into any mission, not just specific tutorial ones. They can have any trait/passive/skill/reaction/normal attack/etc. from any non-legendary character. Instead of having to choose between two options upon rank up, you only pick one option from the entire list- it can't be swapped for a castellia. They can equip any weapon or gear they want. How would you build them?