Neutralise all Vampire/Werewolf powers: A Thread from SOULLESS

[Michael Cule]

I've recently read a novel called SOULLESS and its first two sequels.

It depicts an alternative Victorian age in which vampires and werewolves are openly part of society (and Society too). In addition there are rate people known as Soulless who have the ability to neutralise all vampire and werewolf gifts returning the subjects to baseline human but only as long as they are touching the target!

Now, how to model that in GURPS?

The basic Neutralise power only covers psi and though it requires touch it also requires a contest of Wills and then negates the power for a period of some minutes. How do I do something which affects a whole other suite of abilities and lasts only as long as touch is maintained?