I think this is a really amazing ROM hack for being one from a Generation III game. And I honestly think it has such a lot of potential and will possibly be one of the most amazing ROM hacks out there. Although there are some things I was thinking about when I saw the screenshots.
For one, I don't think the round pads below the Pokémon during a battle look realistic. And I'd also be assuming that Pokémon Sun and Pokémon Moon will no longer have those round pads anymore either (even though I haven't seen the next Pokémon No Uchi at the time of this post).
Also, animations on GBA usually go well with sprites and textures that require less frames. The models from X/Y/OR/AS have their animations used with 3D models. Making them from 3D to 2D sprites would take up a lot of frames, it would mean that the game itself would run slower than usual, due to the amount of frames being loaded into RAM.
Anyways, best of luck to you! I'm sure Pokémon XYZ Version will become something that almost everyone will want to play, by the time it is finished.