Questions
You will be able to travel to different regions by Pokémon, but more info on this feature will be revealed next update.
Mt. Moon will apparantly bring happiness to many fans, but at the moment, it is not in the works.
GYM Leaders in the game will be replaced by some person, but the real questions is "Which ones will be replaced?" Oh, and yes, you will be able to re-battle GYM Leaders. And no, if you were to defeat a GYM Leader who replaced another one, you would not get a badge, seeing how you already defeated that GYM before, dispite the fact that you fought a different GYM Leader. GYM badges are most likely designed, and distributed by the Indigo Plateau, Orange League, etc. to their respectful regions. The GYM leadrs have no control over the design of the Badge, it is all taken care of by the Pokémon Champion Federation. All the GYM leaders can do is give Badges to trainers who sucessfully defeat them in a Pokémon battle, thats all.
I hope that fills you guys in a bit more, and I'm sorry if I missed any other questions.
Captain Arcane