Of course I was just kidding about Allistar not being in that anime, the writers will always find a way to add main characters from the game somehow (Hau didn't appear till the third season of SM, Lusamine in 2nd season of SM), so I would not worry about Allistar not existing, especially since his shyness could work as some sort of ghost plotline or maybe something about Ash's Gengar, who knows
Also, about Melony and Gordie, I just thought of, what if when they appear, there can be some sort of plot about Melony retiring as Gym Leader so Gordie can take over, but it can also be similar to that time when Brock came home and his mother wanted to turn his gym into a water gym, but vice versa instead, and Ice to Rock instead of Rock to Water