This is your new gimmick
Eevee gets 2 new evo, and can evolve by holding an item, making it possible to switch evolutions during the game
Pikachu gets costumes to acquire a second typing and a stab, you change the costumes, you get the idea
No trainer customisation
No secret bases
No Johto but there is Mt Silver, Lillie on top
No Sevii islands but some sort of holidays resort with pokemon minigames like surfing mantine and other stuffs, you access it by a surfing minigame from route 19
No past and future bullshit
Only pokemons that can follow you are pikachu and eevee despite every pokemon models being overworld
You can have NPC following you through the adventure making battles 2v2 or 3V3, you unlock them through the story, Brock and Misty are in it
Story is about rocket team making mewtwo, you rescue mew, then fight robot mewtwo with it, once beaten it loses its armor and go hiding in cerulean game for capture post game
The game allows more freedom, there is no wall or trees blocking each path, you can cut through some dense forest to go to a town instead of taking the classic path
In fact classic paths have trainers, dense natural paths have wild pokemons
The game revolves around fetching quests and saving each town or special characters from rocket team such as in the anime, you can beat rocket team with only one badge
The game is fully in 3D with controlable camera
The pokedex is a smartphone, you can complete it by taking pictures of pokemons instead of capturing them, so you are able to complete the regional pokedex without doing any trades (some books give you infos on pokemons you can't catch)
No national dex
the goal of these games is to really live the adventure as Ash Ketchum in the anime