If only Battle Facility masters are eligible
Then the choices are
>Gen 4 Frontier Brain (Palmer, Thorton, Dahlia, Darach, or Argenta)
>Battle Chatelaine (Nita, Evelyn, Dana, or Morgan)
>Battle Legends (Red or Blue)
>Leon
Leon is too recent to have something like this done to him, Battle Chatelaines are already from Kalos so too redundant, and although still possible, we've got too much Sinnoh recently so probably not any of Gen 4's Frontier Brains, which leaves only the Battle Legends, and Red is a protagonist so if we follow Arceus's plot and have the current protagonist travel back in time (or travel forward or whatever), then Red will be one of the Legends Mew's protagonists, which only really leaves Blue as the option
That is, IF we get another faller, and GF could throw a curve ball and double down on Sinnoh or get the more unexpected choice of Leon, who knows, but the Blue-Kalos connection foreshadowing him being a faller in ZA would be funny
