There’s no way to home brew powers and can we make the damage reduction in the rolls go negative incase maybe we use a weapon that adds a damage multiplier or maybe the enemy has a weakness so they take increased damage
There is no way that I know using the Nexus stuff, but nothing stops you from in your home games jotting down some mechanics and designing your own powers there. I know it’s not the answer you want but it’s the only way I know of at this point.