Not at his present level, but if the RCS were to tailor-make a route for Ganna, he doesn't necessarily need to be among the 3, 4, 5 best climbers to win a GT. A route with 100 km of flat/mostly flat ITT and exclusively mountain stages without massive climbs like Mortirolo, Finestre, Stelvio, Fauniera or Dolomite stage with Fedaia and Giau could potentially promote him to a realistic winning candidate.
I checked the time gaps in mountain stages like that. Typically Oropa 2014 and 17, Pratonevoso 18, Madonna di Campiglio 15, Piancvallao 17 and 20, Oritisei 17 and Cervinia 15 and 18. The time gaps from the best climber to roughly the 10th best climber were typically from about 40 seconds to 1.00 min (Oropa x2, Pratonevoso, Ortisei, Cervinia 18), a couple of times around 1.30 (Piancavallo x2) and two times above 2.00 (Cervinia and Mad. di Campiglio 15).
The competitors would probally be even more eager to attack Ganna earlier in the climbs than is common today if he was to become a GC contender, but if the route consisted mostly of stages like this, I would think there were few opportunites to gain 2-3 min or more. A Ganna who gain 6-7-8 minutes on the best climbers in the ITTs could therefore have a chance at winning the whole thing.