This was going to be a fairly freeform scene, but having a rules mechanism to do the magical equivalent of surgery sounds like a good idea.
Some curses may not be a candidate for this sort of psychic surgery: full transformations might pervade the victim so thoroughly that there's nothing to pluck away. No hope for full mental collapse, such as with Renfields, and that sort of thing. But for memory curses, and other psychic assaults, this could be a valid option.
My initial take is for the GM to determine the Complexity of the "soul curse" as I will call it in this discourse. Then challenge the player to try to generate that many shifts of effect with either Evocation (Spirit/Psychomancy/etc.), or Thaumaturgy (Spirit/Psychomancy/etc.). The GM could scale up or down depending on the desired difficulty, I suppose.
For Thaumaturgy, keeping The Sight open the whole time wouldn't be really feasible, or even necessary. A few exchanges of successful Lore checks should perhaps give the player an idea of the target Complexity for a ritual to remove whatever soul curse had been placed on the target.
For Evocation, though, generating that much effect could be really difficult. Perhaps Taking Out the soul curse (generating enough shifts of effect for a final "push") would be the best option. Especially since the player will be fighting the horrors in The Sight every round. This would resemble Thaumaturgy at the speed of Evocation, though in this case the player would be getting down and dirty, grappling with the soul curse, rather than "banishing" it such as would make sense with a Thaumaturgic solution.
Should a soul curse fight back, perhaps dealing damage to the victim for any failed checks? Or should that vary between soul curses? Maybe specify that for +2 Complexity, the soul curse will roll against any attempts to remove it, using the original caster's Lore check (pure Lore, not with any focus items or ritual Declarations).