You appear to mix up the complex (HoH:S p.93f) Hermetic Virtue Leper Magux being a "mystic legacy passed on from Tytalus to Hariste's line" with the way Tytalus has acquired leprosy before from Guorna's dying breath.
That said, in your saga you can allow modifications to the Virtue Leper Magus (see your OP for its definition) as you see fit.