Ah, I just had to respond to this. I had an idea to do a fic like this about three years ago, but never got around to it.For a while now, I've been thinking of something like a sort of Jurassic Park in Pokemon, though I haven't got much other than that. The original idea I had was the park would have Pokemon they way they were before being trained by human, basically ferocious and bloodthirsty. Now though, I kind of want to do it with Fossil Pokemon, as that would probably fit the overall 'Jurassic Park' theme better.
Anyways, I would think that it would be more original if it were before the Pokémon had been trained, since using the fossil Pokémon seems entirely too expected, and rather limited in it's scope, unless you plan on having variants of the fossil Pokémon due to extensive changes to their genetic makeup while creating them.
If you do it with untrained Pokémon, will it be a world that has just discovered Pokémon, or will they have their own Pokémon but certain species are considered too violent/powerful to be trained, so they are instead used in attractions worldwide?
Or have a world were people have found fossils of Pokémon and are now resurrecting them because curiosity and greedy corporate-ness (so a AU were Pokémon once existed, but have now been discovered. You wrote a one-shot detailing something like this, yes?)
Going off that last thought, they could discover that some Pokémon are fairly friendly, while others... not so much. The Pokémon could also be found to be quite intelligent, enough so where they can understand commands with proper training. This causes concern as to whether or not they can be contained and from there it gets into the Jurassic Park theme with the raptors and whatnot.
As a huge fan of Jurassic Park (both the books and the movies), I wouldn't mind seeing a fic on here based on it, even though I've already seen a few Pokémon/Jurassic Park fics before. If you do decide to make one, I would be interested in assisting you with writing it or providing ideas/feedback, if you'd like.