What would happen to the anime-exclusive Kanto towns that Ash and co first visited? Remember the school of hard knocks? The episode where A.J. had a 99-win streak with a Sandshrew? Or Dark City? The one with the Yas and Kas gyms? If anything, they're best off as the places these World Tournament competitors come from. Yas gym's Scyther and Kas gym's Electabuzz if they appear at all would probably already be a Scizor and Electivire respectively. And A.J. would probably have several Pokémon alongside that same Sandslash. A World Tournament would probably feature exactly 1,024 Trainers including Ash, his main rivals (Gary, Paul, Trip), random COTD's like A.J., and even gym leaders such as good old Brock and Misty. I have a feeling who wouldn't be there: Giovanni as he's busy with TR; maybe Iris as she may take on other dragon trainers in the Blackthorn tournament if there was one. I would guess at the best location for the World Tournament (if in Kanto or Johto) as either Indigo Plateau or Silver Town.