I think ev training is one of the good thing in pokemon games bc if there is something like this we wont want battle in wild to ev train we will just battle to earm money. And after making all good pokes we wont battle in wild and this game will be bored. So if we can ev train easily like speed ev train by making a place where most of the pokemons give us speed (not all) and we have to pay money to enter this place then it will be better may be.