Don't assume there is automatically a hack of a game that is exactly how you want it.
There is no hack of Black/White that turns the game into Ruby/Sapphire/Emerald. There is no way to edit the overworld of the game due to the immense amount of 3D objects.
The closest to what you want would be a hack somewhere in this very subforum that turns Diamond/Pearl/Platinum into Ruby/Sapphire/Emerald. However, I don't know if it was ever finished or a patch was ever released.
Though if you can wait, there will eventually be a remake of Ruby/Sapphire made for the 3DS. Or at least it looks that way.