"or just let them use any attacks that they can learn or perhaps something in between."

That's what I'd prefer. I mean, I come up with pretty brutal, yet creative combos. Using Takedown and Double Slap should be something all Pokémon should be able to use instantly and stuff. So yeah, I'd rather the Moves be completely free and creative, as long as we use common sense. (I.E Having your Pokémon use Hydro Pump when they're a fire-type.)