Kamara Taj would be the best plastic due to their ability for the Mirror Dimension. His ability is highly destructive and the Mirror Dimension would be a good training ground and way to separate fights from the real world.
I hope that MC goes all over the planet be it Secret Places, Pocket Dimensions, Incredible Master Individuals (like BRUCE WAYNE did but more extreme) to be a person with the "TRAIT: MASTER OF ALL"
Most Fanfics show the MC enjoying his freedom and not liking joining an organization, and like almost all the protagonists have this trait, it looks like ctrl c ctrl v to me.