Most of what you wrote wouldn't be neccessary. Different cries because one bit cry is not enough? Why? They freshened up on the old cries in X/Y for the first time, and gave Pikachu a voice. I would be perfectly happy with that.
Now, I don't know how they would solve the encounter problem, should it be random encounter or not? I don't know how Colosseum/XD did it, I guess it was random. But this would be possible. The whole world wouldn't havw to be rendered at the same time either, if you are at a sea you don't need to see what's on the other side of a big mountain (like in Sinnoh). I don't think every 700+ pokémon would be featured at the same time either, is every FFXIII enemy/creature featured at the same time? No.
What I'm saying is that it would be perfectly possible to make this game and still fulfill or exceed expectations.
Yep.
