I think Wash would be much better suited for the role of the power nuke than Touma. Wash's power nullification has far better range and can keep her powerless for two minutes (which is the equivalent of a century in a fight) compared to Touma's almost nonexistent range and power shutdown duration. Touma would work better as a defensive wall along side North and a trump card against any unexpected bullshit.

For example, North can focus on keeping the four year old safe with his bubble wrap shield while Touma sticks with Wash.